I agree, I don't think anymore than 10 thou is necessary. I would say start with 5 thou & go from there. Won't really hurt if the clearance is on the larger side but I would say keep it as minimal as you can, not only to adjust TIR to the lowest you can but also considering if you will ever use the adjustable chuck to dial in parts.
If you do use it like that as some do like for production work, you would have to determine how much clearance you would want. I don't use my adjustable chucks like that, I only adjust for lowest possible TIR for the clamping range that I use the most. For example, I adjust my TIR at 1"dia with my 6 jaw Set-Tru & 1.5"dia with my 3 jaw Set-tru. TIR won't be accurate through the whole range of the scroll but if it's a well made chuck it should be pretty good. My Bison chucks are pretty damn good.
I say minimal clearance as needed only cause it will help save you time adjusting TIR whenever you have to disassemble & reassemble the chuck. May not be that often but you should clean it periodically.
Sorry for the semi hijack but here's another subject that people seem to have different opinions on. Whether or not to leave the adjustment set screws tight or loose after adjusting TIR. I leave my adjustment screws tight. Some people say that after you adjust TIR & tighten up the chuck mounting bolts, you should back off the adjustment screws. I don't agree with that.
For one, leaving those adjustment set screws loose, there's a chance of those set screws backing out & flying out. Unlikely to happen & you should notice any of them backing out before they could fly out. Leaving the set screws tight gives you less chance of the chuck from being bumped out of true, the very disadvantage of a Tap-Tru. But I've never had on of my Tap-Trus get bumped out of alignment.
My Bison Set-Tru check have pretty large diameter set screws, almost twice the size that were on my old Gator adjustable chuck. I never had a problem with the smaller set screws on that Gator chuck but there must be a reason why Bison choose to use such large screws.
What say you guys?