Doing a build like this and not doing a proper dry build always had the potential for disaster and sure enough, 1 day, it has bitten me on the arse.
The problem was that it was all becoming a bit time critical so I didn't wait until I had the actual engine with its actual ancillaries before I stripped the frame et al for powder coating, painting, etc.
Anyway, the engine and gearbox went in beautifully right until the time I thought I'd put the carbs on to admire it. Carbs? No probs, velocity stacks? Not a chance. The stacks interfere with the diagonal frame braces, particularly on the right (rearmost cylinder.
I could shorten the inlet stubs, I could shorten the velocity stacks but both of those options (and I've checked with RM) would trash it's mid range performance. In an ideal world a set of cranked inlet stubs - so that the carbs sat almost parallel to the crankcase would solve the problem. Not ideal from an inlet tract point of view, but I'd be tempted to try it. I mean, airheads inlet tracts aren't exactly ideal anyway.
Anyway, I have retired to sob pitifully and consider my options...