There's a few pipe building programs out there, even free, one from IWT racing, you need to be able to provide the program alot of info, then if you get that part right you need to make the cones, there are also free prorams for that, still a major undertaking. people spend a lot of time building pipes that should work then making revisions and tweeks, I may attempt it some time but I don't know when I'll get that sort of time to screw with it, would need a dyno along with other data acquisition systems to really tell if you were making head way. kinda off topic here
original topic was home porting, I say go for it, just take it easy, smooth out casting transitions and imperfections, Here is some info from Eric Gore, on the cylinder:
"The hook angles of the rear transfer ports should be filled with epoxy so the transfers are aimed at each other instead of towards the exhaust port. the narrower the port, the sooner the smoother the low end power. The minimum chordal width of each rear transfer port is 10mm. Raise the exhaust port 1.5mm and widen the two ports 4mm on each outer edge. The steel sleeve should be matched to the aluminum casting because it is very rough from the original manufacturing process. Polish the port edges with fine grit sanding paper. that will improve piston and ring life."
Let us know if you do any of this and how it comes out, I have not been able to find this info on Eric's site lately, I think he no longer is interested in giving away his secrets.