The best tool for making pipes is experience, by this I mean that over the years all pipe builders make plenty of pipes that didn't work exactly as planned, some that worked good after being modified and some that just cracked straight off and because of the time and effort involved in this they don't like sharing thier secrets with others.
I know a pipe builder who records the exact measurements of all of his good pipes and there have been heaps of them, he includes the make and model of the bikes and over the years he has built up a history of what works on early and later models, because the pipe that suits a 1960s Greeves 250cc wont necessarily work on a 1980s Suzuki heaps of other things come into consideration.
Zane