Known Bugs & Shortcomings.

Immediate solution Fixed
VSMAPED:  You can't transform 3-plane maps into 2-plane maps, or vice versa. Accomodate the 2-plane maps to the wanted number of levels and insert levels from the 3-plane maps one by one. Likewise for 3-plane maps.  
VSVGAED: No chunk may have 0 (zero) bytes or VSVGAED might crash. Not a big problem, any text will consist of at least 1 byte.