I was trying to use Mapwel for a while for the custom types, but ran into the problem of not being able to run my image files into MapSource, where all the rest of my maps are. Fortunately, Mapwel will merge their img files into the existing gmapsup on the device. So you can load all of your non-Mapwel maps from Mapsource and the use Mapwel to integrate the ones that can't use MS. Merging is slow, but it works.