Below is a PM that I got a while back from Mini SSS on the hdforum site.
I'm using Khrome Werks +2 Sweepers. The machinist I used reamed out to 7/8 and because of the lenght of the grip area had to follow up with a 7/8 drill bit. He said he wouldn't recommend doing it again because the bar thinness and heat warped the bars a bit. I had to smooth out the interior of the bars with a hand drill, rod and sand paper. The exterior was no longer truly straight. Fixing it involved draw filling and shoe shine sanding it to get the new throttle grip to turn freely. It was a lot of PIA work. I hope you find a machinest to make the project easier for you. FYI, the air cushion type grips (ISO GRIPS) will not get as hot as ones that have full contact with the bar. There is a warning about this in the installation instructions. The TBW is what makes reaming out necessary. I believe the TBW slots at the end of the throttle end of the bars are what made the reaming difficult, because of grabbing of the edges of the slots with the drill and reamer edges.
It is a good day today. New Heat Demons , Iso Grips. +2 Sweepers, Elf 2125X amplifier. J&M 7.25 speakers work and the bike actually started since I started this project 3 weeks ago.
I know this is a lot of babling but I hope it helps with your future installation. BTW, The guy I called at the demon factory was very helpfull with a bad circuit board issue. He sent a new one within a couple of days.
If you have any more questions, feel free to ask. A lot of other guys on this forum were very helpful to me, so glad to pass it on. Cheers. John
I would love heated grips but not sure it's worth it. Maybe some day