RE: 7.5 Hydro Design
Not knowing what kind of hull design your looking at, I'm going to throw out some generic numbers:
Length 36"(+2)
Width 18"(+1)
Tunnel 9.75"(+1)
After Plane 15"(+2)
Engine Just behind the sponson transoms
Prop Weight 1.25lb(+.25)
Hope this helps