Pulley Swap

So im getting a MST-206 swapped into my tractor, and i've been thinking about a double pulley system, where a clutch operates each set of pulleys and I can select a high gear and a low gear from there. I was wondering what the highest pulley swap I could run on it would be? Im planning to run 20 inch somewhat aggressive tires and a 12HP briggs(if i can get it running). I also want to make sure that theres no limitations on a low gear pulley swap either, because I dont want to break anything.

well a 1:1 ratio is pretty good with 4 inch pulleys for a romper. a lowered racing tractor would be more like 2:1. I think the description kind of hints at a romper. if 1:1 isn't enough, a five inch front with a 4 inch rear is about what i run and love it