I am going to machine down the standard flywheel with the hope that it will have enough metal thickness to provide a flange to take the new extension, which I will turn up. The extension will have a mating flange with a spigot and be fixed with four axial studs. The flywheel is a kind of plastic/alloy combination; it is hard to tell if this will do the job before I start reducing it down. There is every chance I will have to start from scratch.
Can one of you experienced engine builders describe a step by step set of instructions of how to make the extension please? Any drawings or picture will help. At this stage, I can't see how it can be done without machining the taper to fit the crankshaft, then turning it around and do the other end. I have no experience in dialling in a job like this would require, but have seen it done.
Also, what alloy is suitable?