OK all...

Re: fitting SG front standard...I found I can take the big flange off, resulting in a smaller barrel diameter...for future reference, like SG lens boards, this may make things easier.

Re: distance from film. It was on a rigid body camera. I was told 100 mm flange distance (registration?). The helicoid is marked 3.5-18 feet, so even at 50 mm or 150 mm, the helicoid does the movement. But obviously, the difference between 18 feet and infinity then amounts to a shim or tiny spacer...I suspect it'll be interesting tweaking that. So, internal or external movement aside, the math should still rule.

Hmmm, I was thinking (maybe I wasn't) it would be a bigger spacer than that, and envisioning short normal and long positions on a rigid mount...normal = 3.5-18 as scaled, shorter for ?-infinity scale to be determined and zoom vs focus behavior to be determined, and longer for however much closer than 3.5 feet I could get.

I was guessing 5 mm for experiment's sake, no calculation, and now applying 150 mm in place of 150 mm I get 154.2 for 18 feet...so this all helps give me some perspective.

Thank you for the 'grounding' info.

Time to start building...

Oh, Dan, I shot a roll of the 620 film from ancient Rome this weekend in the old Vollenda.