Hi, Chris. My two centavos worth.
Muzzle pressures are pretty low - say 400-500 psi - so it doesn't take a lot of wall thickness to contain them. I'd be more worried about thin muzzle walls being subject to denting. There should be no line if you say so to the craftsman. Your call on choke constrictions as you know how you hunt and shoot.
If you decide to pattern, please, oh please, use Dr. Jones's "Insight" pattern analysis program. In so doing you will actually know for sure that you understand your patterns. I can testify in person that manual analysis of patterns is a lengthy, time consuming process but it must be done to actually "Know" whatchagot. There is some "pain" (read learning curve) involved in Insight, but it really is the key to using pattern analysis to "know." Patterns are way too complex and variable to do anything but statistical analysis.
A fixed choke tube should change the gun's MOI very little. Tape an ounce weight to the muzzle and see if you can tell any significant difference. If not, don't worry. If so, let me know and we can run a projected new handling number set based on the gun as it sits.
Good luck with it.
DDA
