issue with canvases on stacked panels

app=CreateWindow("CS_TBL does :(",0,0,640,480)

panel1=CreatePanel(4,4,256,256,app):SetPanelColor panel1,200,100,100
panel2=CreatePanel(64,64,256,256,app):SetPanelColor panel2,100,200,100


; try one canvas at a time, 1 or 2 ... it will work ok!
;
; then try both.. :(
;

canvas1=CreateCanvas(4,4,248,248,panel1)
;canvas2=CreateCanvas(4,4,248,248,panel2)

Repeat
	WaitEvent()
	If EventID()=$803 quit=True
Until quit
End

Is it a bug, or a feature?

In both cases: can it work flawlessly? :)

Idea is that one panel shows a (mapeditor-)map, the other shows (mapeditor-)tiles. And some key or $203/$205 event on the back-panel brings forth the backpanel, and vice versa..