help on flowing piaggio cases

hi in a couple of days im goin to be splitting my piaggio engine to replace the left hand side engine case do to 8 or 9 threads have gone that hold my trany case on so i thought i might aswell try flow my cases whilst ther split could any one give me some pointers on how to match my cases to my malossi sport 70s
thanks

 

anyone ???

 

i swear people r stumped when it comes to this lol

 

I would put cylcinder on with just the two stubs and mark out the edges of the ports roughly so you know how much to take off...