Thanks - your pictures and suggestions were pretty much what I'd been thinking.
I've got about 7 1/2 - 8" to the water in the trap. So it would seem I've enough room to fit in the adapter and keep the new drain low enough. Another question with this - should I refill that broken out area with something like pea gravel?
I hadn't given much consideration to drain types up till now. I just wanted one that would 'work' and not be too much trouble installing. Seems I'd have to order anything other than what I showed above. I'm not sure of their manufacturer, the local go-to plumbing supply as well as Home Depot seemed to only have those in stock. I'm open to suggestions. This shower is in an extra bath and I want it nice but nothing showroom/Fine Homebuilding type. Your work looks gorgeous. I'm planning fairly basic tho with a small seat and a nook above which I think is within my skills. I'm putting in a mid range basic shower head and controller, of course the old one wasn't anti-scald anyway and I'll redo a bit of the old inlet water lines which were rather creatively placed. I've got the time and try to not rush, ask plenty of questions and think things thru and try to keep costs down that way.