As far as I know, the MP7.5 and most other buggies has "proper" gearing (either 14/48, 13/46, or 14/46). Lighter clutch springs would help as well and perhaps try a 12 or 13 tooth clutchbell. About your alum clutch shoes, don't expect long life out of them unless you take the clutchbell off and scuff the clutch shoe sides with a fine steel wool periodically.