Go tech parts are not reccomended to use in Rossi engines. Just because the parts fit together does not mean the engine will run properly. You are talking about something that will spin 30k, having a tolerance off by a thousandths will cause serious damage.

Rabbidsquirel the rear bearing in a P5X is not the same size as the Go Tech rear bearing.

Also how tight a sleeve fits in a crankcase is important to performance, the sleeve needs to be placed in a crankcase it was designed for.