There are many variables to head porting when you add valve size and cam specs into the mix. My advice is to save your pennies and pay a known builder to port your head so it performs exactly how you want. There is not one magic porting design for all riding styles, some give more torque, others give more HP, and some just make lots of room for nitrous. Doing it yourself may save you a few $$ but it will be a crapshoot that your garage porting will maximize the rest of your engine mods. If you decide to port it yourself, don't bother with oversize valves.