I'm back with my results. Stars resolved at 70mm is 1! only JUST too. (with 10 mins dark adaption)
Easily resolvable at 150mm. At 120mm easily resolvable with only a couple of mins dark adaption. Good call Atalas!
Judging by all that, I'd guess a 4" aperture minimum to resolve it. Now I need a variable aperture mask rather than making a dozen of them at different sizes.
