Possible to create a new window class for gadgets?

Hmmm...it seems an additional style is needed...otherwise the OpenGL viewport gets painted over when another window crosses over it...isn't there some kind of a "Save Bits" style you can use? I can't find any win32 constants like that...

...I tried this, to no effect. Hwnd is the panel:
style=GetClassLong(hwnd,GCL_STYLE)
SetClassLong hwnd,GCL_STYLE,style+CS_SAVEBITS