I'm not a specialist as Ameybrook, but I think that if the frame is suspension corrected or not, doesn't be a problem for doing a C26.
Chris have to cut the front part of the frame. So, he can change the geometry .
On other hand, for doing a JT replica, 1" headtube, but you have to respect the 73° headtube angle
Thanks for all concerns. I haven't got started on the build yet. All parts are in place. But we just bought a new house last month, so all bikes and bike stuff are packed and temporary stored waiting to build a proper workshop. First comes a home cinema/HiFi room
This means I am off the retrobike build for some months from now, but the first thing on the list is build this ultimate FRO build. I have not hold back for any of the parts spec - it will be a knocker! It will not be a catalog correct build or a historical rebuild. The paint scheme is also sorted - and it will be a blower and not so Yeti - but with some Yeti hints ;-)
So happy Easter holidays - and seeya all later...
Keep on riding safe!
PS a couple of you are waiting for some parts - they are keept aside and will be shipped/sorted as promised. Theese last 4 weeks have just been new house new house new house for me.