My Sherpa came with a 13-tooth front sprocket (stock is 14) and it definitely gave the bike a more 'agricultural' feel that would probably be well-suited to trials-type riding. I switched to a 15-tooth sprocket because most of my riding is on the street and the gearing was just too low with the 13-toother.
The bike is very narrow and could probably be lightened a bit by removing whatever you didn't need for trials riding (cosmetic plastics, pillion pegs, lights, mirrors, etc.).
Bikeless for now.