You will find it hard to get a nice belt height adjustment (1-2+mm) above the secondary . This would be with c/c being right on and in "spec" and a new belt at new spec demensions. Thats is just the way it is with yamaha belt lengths. I feel they are just a bit to short if ya ask me .I will measure the belts on the shelf at dealers to look for the longest possible to help with a good belt adjustment. As far as the least # of washers .... you should always leave one in place. More washers= higher belt less=lower belt height. Best tip I can give is to adjust the belt so the track just begins too"creep" (turn forward) with the sled idling on the stand. The sled shows even after a FULL SHIFT run in perfect conditions and a aftermarket helix cut to allow the secondary to completely open that it could still could shift out a bit more, closer to a 1:1 ratio. Know that gearing also can have an effect on this FULL SHIFT topic. As ya can tell .... this is a pet peeve of mine, hope I didn't over do it for ya.
Happy trails.
Rich Kay.