don't over calculate, what works on paper doesn't always work on mopeds (that the funny thing about mopeds as opposed to big bikes).
measure 10 times and cut once and u get one result.
measure once, cut 10 times and u get 10 results to choose from.
the best experience is 1st hand, practice practice practice...
Be fore you get ur kit sorted out you should throw on a cheapo pipe, grab the 60-70 range of bing jets and get up in ur stock shit with the dremil, you will learn alot with very little $$ and gain some valuable hrs in ur motor.