PNG output is clipped compared to drawboard

[fdebijl]

This drawboard:

Results in this output, where the top 50 or so pixels are clipped:

Probable cause:
Either the renderbox is too small, or the SVG's are too large. The SVG's and the renderbox both need an absolute value in pixels for their width and height, so either one of those needs to be adjusted dynamicallly in SaveAsPNG()