I am onto my 2nd Mint tractor having used it with a Rega RB 1000 and now with a Triplanar on a Michel Orbe TT. The advice/comments above are spot on : take the tonearm as far as it will physically go in both extremes ie towards the spindle and the outermost part of the platter.You are correct that given the mounting position of the Triplanar and the arm rest there is no way that you can get the stylus to rest on the edge of the Mint arc beyond the platter. I don't think thats too important, if you have the overhang correct on 2 extreme points on the arc you should be mid way to vinyl heaven; sort out the null points and you are truly there.
Cheers
Cheers