i whould go with a 10" notch to be safe and trim down so you dont have this big a$$ gap between the axle and notch (IMO i think it looks retarded when ppl over notch there ish)
be sure to leave a lil extra so when u dump the back to drag you will have some extra room for the axle to move and not ride the frame . i have a lil formula to figur where the notch should be on the frame if you want it email me at
mazdwgdrgr@aol.com