Paul, I dug out the instruction sheets for my OS FT 120 II and it specifies a .04-.10mm valve lash set cold. I could not find anything about cam timing, however if your engine runs, it could not be off more than a tooth, if at all. With one cylinder at TDC, you should be at the center of the "valve overlap period" on that cylinder. What it means is that at TDC both valves should be very slightly open and if you rock the crankshaft back and forth, you should be able to see this while looking at the rocker arms, one will close while the other opens, rock the other direction and the opposite will occur. If this happens @ TDC, the timing is correct.
I think you should seriously reconsider powering a helicopter with a twin glow engine. While losing a cylinder in a airplane may not be a big problem, because the engine is still running, just at reduced power, this would be a disaster in a heli. I guess this is why you don't see many heli's with this engine configuration.

Mike