There's no built-in way to do that at the moment. Your best bet is to call some windows API calls (FindWindow I think) to get the window handle of the R4 window, then set it to not have borders and finally every time your canvas moves on the screen position it over where the canvas is.
I don't know how you call the Windows API from Java, but there must be some bindings + examples around somewhere. It sounds a bit of a crap idea, but actually resized windows are basically what heavyweight AWT objects are anyway.