I'm well out of practice with machine thread cutting Pat, in fact I can't even remember a thing about it, gearing,angles etc
been trying to find a book to relearn it all again but nothing in the local shops, have to send off for one I guess.
Top cap depends on how high you've raised the bars, a lot like me have probably just raised them so they are flush with the top of the tubes, suppose another few mm wouldn't matter and give a little bit of a recess for a plug to fit in but wouldn't be enough for an O ring though, looks like the usual small blob of silicone would have to come into play again.....join the queue.
Looks like I can be kept busy, I did make a couple of spacers to go under my raised bars to fill the gap though just to see, only had 2" bar though, 2.5 will be better then it will be flush with the edge of the bar clamp.
95% of all Harley Davidsons ever made are still on the road... the other 5% made it home.