How to add custom widgets in wxglade

Question

I have an app that I made with wxglade. I've added a mediacontrol to be able to play mp3:s. Without the mediacontrol the app starts with a frame that is 800x600px. But when I add the mediacontrol, the frame is very small. I believe this is because I've not added it to a sizer. But do I have to do that? The mediacontrol isn't supposed to show anything anyways.

So, my question is, how do I add a mediacontrol to my app without (a) breaking the possibility of updating the gui with wxglade and (b) losing the ability to start with the right size?

If I can I would not put anything between the # Begin wxglade and # End wxglade. Because then it will be destroyed if I change my gui with wxglade (according to earlier tests anyway).

Edit: The code snippet I supplied doesn't add anything of interest. I also edited the question to be more clear so other people with the same question can find this answer.