the Rossi 61 RE or SE will fit just fine in either the P7 or The P8, they use the same bolt pattern as the OS 60/61 cases, using anything less that a 11x10 or the like is a waste on the long-stroke versions, i use 11x10 on the shortstroke versions as well with the macs quite pipe set long, i own both the hangar nine p7 and have it fitted for the rossi's, and i have 2 P8's as well, plenty of room there as well..

the VP mod actually knife edges the leading edge of the crank counterweight and also puts a relief cut on the edge of the crank-bore to unmask it when the con rod moves across its face...standard fare on car and boat motors.

with head shims there is no reason not to use 30-50 nitro in the rossi's a colder plug and head shims will wake them up with 30-50 nitro, they are every bit as strong as a YS if loaded with same nitro content.