Hi Breadcrumb. Sounds like you are sorted with the skills so just get stuck in. I only do a bit as a hobby but drop me an email and I’ll give as much info as possible.
Apologies for going a bit OT, but quick answers to the questions for those interested – and probably convincing everyone just how little hassle and good value a far east frame (or a Shand!) is:-
I made a jig – but can be done with just a flat surface and V blocks.
Generally mix and match tubes. For the more basic tubes there is more choice in diameters than wall thickness.
Plain 1.5m lengths of cro-mo in 0.8 – 0.9mm wall are around £10-£15 +VAT (various sizes from 8mm to 44.5mm). Much cheaper than aero spec 4130 / T45. Great for practice and I often use for seat tube and rear stays. http://www.framebuilding.com/Spare%20Tubes.htm
A mid range butted top or down tube like Zona is around £20-£25. Columbus do longer 750mm Zona down tubes for 29ers in 35 or 38mm. I’ve not built for anyone heavy so generally use 32mm tt and 35mm dt. For reference an Inbred that passes the fatigue tests for a heavy rider uses 35mm tt and dt (dunno what wall / butting but fairly chunky). http://www.framebuilding.com/ZONA.htm
Tube bending is done cold and can be tricky – no real substitute for tooling. Bending the ST is very difficult – tube rollers are the correct way to do it. I pack with sand and use this plywood contraption – leaves a few ripples and sometimes kinks / scraps the tube so far from ideal. Just about manages 24 deg bend. 38 deg bend in the 2nd photo shows a kink.