Looking pretty sharp, Ravells.
1) Did you start with the map or make the terrain first and then paint onto it? Alas, I recently purchased CS4 but did not pony up for the Extended version.
2) Does your terrain have any "actual" geometry or is it all done with sub-d?
I'm a Silo user as well...my favorite modeler for the past couple of years. I was trying to do something similar with my Haibianr map but took a different approach; one that didn't work out as nicely as yours. I used my sketched contour lines as a guide for creating the mesh, but they were pretty non-scientifically drawn and the resulting landform wasn't all that attractive. I also gave it a shot in an older-than-current version of Bryce with not so great results. I may have to give your way a go.