Thumbnail inside sizers

I’m having trouble with thumbnail1, thumbnail2 and thumbnail3, they are too small and I’ve been changing the flags from the sizer trying to enlarge them but I’m been unable to do so.
I have no trouble if I get rid of t2Sizer and t1Sizer and put them directly on topmostSizer, but I don’t want that, so what am I missing?

Here is the working code, you just have to change the paths:

from argparse import _AppendAction

import wx
import wx.lib.agw.thumbnailctrl as TC
import cv2
import os
import glob
import wx.stc as stc
from time import sleep

class MyForm(wx.Frame):

    def __init__(self):
        wx.Frame.__init__(self, None, wx.ID_ANY, title='Test')

        # Add a panel so it looks correct on all platforms
        self.panel = wx.Panel(self, wx.ID_ANY)
        bmp = wx.Image("#PATH_TO_IMAGE\\test.png", wx.BITMAP_TYPE_PNG).ConvertToBitmap()

        inputTxtOne = wx.TextCtrl(self.panel, wx.LEFT, '', size=(1500, 50))
        inputTxtOne.SetFont(wx.Font(15, wx.SWISS, wx.NORMAL, wx.NORMAL)) # Font & size ARIAL

        thumbnail1 = TC.ThumbnailCtrl(self.panel, imagehandler=TC.NativeImageHandler)
        thumbnail2 = TC.ThumbnailCtrl(self.panel, imagehandler=TC.NativeImageHandler)
        thumbnail3 = TC.ThumbnailCtrl(self.panel, imagehandler=TC.NativeImageHandler)
        thumbnail1.EnableDragging(True)
        thumbnail2.EnableDragging(True)
        thumbnail3.EnableDragging(True)
        thumbnail1.ShowDir("XXXX") #Link to image folder

        # ################VID################ #

        fr = 150
        v_files = glob.glob(os.path.abspath(
            os.path.join("#PATH" + "\\Videos", "#FolderName", '*.mp4'))) # Example: C\Folder1\Folder\Videos\FolderName
        for i in range(len(v_files)):
            cap = cv2.VideoCapture(v_files[i])
            total_frames = cap.get(7)
            cap.set(1, fr)
            ret, frame = cap.read()
            cv2.imwrite(v_files[i].split(".")[0] + '.mp4.jpg', frame)
        # print thumbnail.GetZoomFactor()
        # TODO On the receiving end, when I read a jpg file which does not exist I have to search for the mp4
        thumbnail3.SetZoomFactor(1.8)
        thumbnail3.ShowDir("#PATH") #C\Folder1\Folder\Videos\FolderName
        topmostSizer = wx.BoxSizer(wx.VERTICAL)
        topSizer = wx.BoxSizer(wx.HORIZONTAL)
        t1Sizer = wx.BoxSizer(wx.VERTICAL)
        #t2Sizer = wx.BoxSizer(wx.VERTICAL)
        self.image = wx.StaticBitmap(self.panel, -1, bmp)
        topmostSizer.AddSpacer(20)
        topmostSizer.Add(self.image, proportion=0, flag=wx.ALIGN_CENTER)
        topmostSizer.AddSpacer(20)
        topmostSizer.Add(inputTxtOne, proportion=0, flag=wx.ALIGN_CENTER)
        topmostSizer.AddSpacer(20)
        topmostSizer.Add(topSizer, proportion=0, flag=wx.ALIGN_CENTER)

        t1Sizer.Add(thumbnail1, proportion=0)
        #t1Sizer.Add(thumbnail2, proportion=0, flag=wx.ALIGN_LEFT | wx.SHAPED | wx.EXPAND)
        #t1Sizer.Add(thumbnail3, proportion=0, flag=wx.ALIGN_LEFT | wx.SHAPED | wx.EXPAND)

        topSizer.Add(t1Sizer, proportion=0)

        sleep(0.8)
        for i in range(len(v_files)):
            os.remove(v_files[i].split(".")[0] + '.mp4.jpg')

        self.panel.SetSizer(topmostSizer)
        self.panel.MaxSize
        topmostSizer.Fit(self)
        self.Maximize(True)

    def onOK(self, event):
        # Do something
        print 'onOK handler'

    def onCancel(self, event):
        self.closeProgram()

    def closeProgram(self):
        self.Close()

class Log(stc.StyledTextCtrl):
    """
    Subclass the StyledTextCtrl to provide additions
    and initializations to make it useful as a log window.

    """

    def __init__(self, parent, style=wx.SIMPLE_BORDER):
        """
        Constructor

        """
        stc.StyledTextCtrl.__init__(self, parent, style=style)
        self._styles = [None] * 32
        self._free = 1

    def getStyle(self, c='black'):
        """
        Returns a style for a given colour if one exists. If no style
        exists for the colour, make a new style.

        If we run out of styles, (only 32 allowed here) we go to the top
        of the list and reuse previous styles.

        """
        free = self._free
        if c and isinstance(c, (str, unicode)):
            c = c.lower()
        else:
            c = 'black'

        try:
            style = self._styles.index(c)
            return style

        except ValueError:
            style = free
            self._styles[style] = c
            self.StyleSetForeground(style, wx.NamedColour(c))

            free += 1
            if free > 31:
                free = 0
            self._free = free
            return style

    def write(self, text, c=None):
        """
        Add the text to the end of the control using colour c which
        should be suitable for feeding directly to wx.NamedColour.

        'text' should be a unicode string or contain only ascii data.
        """
        style = self.getStyle(c)
        lenText = len(text.encode('utf8'))
        end = self.GetLength()
        self.AddText(text)
        self.StartStyling(end, 31)
        self.SetStyling(lenText, style)
        self.EnsureCaretVisible()

    __call__ = write

class MyTextDropTarget(wx.TextDropTarget):
    def __init__(self, window, log):
        wx.TextDropTarget.__init__(self)
        self.window = window
        self.log = log

    def OnDropText(self, x, y, text):
        self.window.WriteText("(%d, %d)\n%s\n" % (x, y, text))

    def OnDragOver(self, x, y, d):
        return wx.DragCopy

class MyFileDropTarget(wx.FileDropTarget):
    def __init__(self, window, log):
        wx.FileDropTarget.__init__(self)
        self.window = window
        self.log = log

    def OnDropFiles(self, x, y, filenames):
        self.window.SetInsertionPointEnd()
        self.window.WriteText("\n%d file(s) dropped at %d,%d:\n" %
                              (len(filenames), x, y))

        for file in filenames:
            self.window.WriteText(file + '\n')

class FileDropPanel(wx.Panel):
    def __init__(self, parent, log):
        wx.Panel.__init__(self, parent, -1)

        # self.SetFont(wx.Font(10, wx.SWISS, wx.NORMAL, wx.BOLD, False))

        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(
            wx.StaticText(self, -1, " \nDrag some files here:"),
            0, wx.EXPAND | wx.ALL, 2
        )

        self.text = wx.TextCtrl(
            self, -1, "",
            style=wx.TE_MULTILINE | wx.HSCROLL | wx.TE_READONLY
        )

        dt = MyFileDropTarget(self, log)
        self.text.SetDropTarget(dt)
        sizer.Add(self.text, 1, wx.EXPAND)

        sizer.Add(
            wx.StaticText(self, -1, " \nDrag some text here:"),
            0, wx.EXPAND | wx.ALL, 2
        )

        self.text2 = wx.TextCtrl(
            self, -1, "",
            style=wx.TE_MULTILINE | wx.HSCROLL | wx.TE_READONLY
        )

        dt = MyTextDropTarget(self.text2, log)
        self.text2.SetDropTarget(dt)
        sizer.Add(self.text2, 1, wx.EXPAND)

        self.SetAutoLayout(True)
        self.SetSizer(sizer)

    def WriteText(self, text):
        self.text.WriteText(text)

    def SetInsertionPointEnd(self):
        self.text.SetInsertionPointEnd()

# Run the program
if __name__ == '__main__':
    app = wx.App(False)
    frame = MyForm().Show()
    #import wx.lib.inspection
    #wx.lib.inspection.InspectionTool().Show()
    app.MainLoop()

Thanks for the help!