Mature Metal discussion

I’ve just received my Jailbird and I’m loving it. I might want to tweak it a little in sizing, and I was wondering what things can be modified and what can’t. I was just going to send in an email, to MM because they are so great about responding, but I thought doing it here might answer the questions for a bunch of people instead of just me. So what can change and what can’t? Base Ring Diameter Base Ring Shape Cage/Ring Gap Cage Length Cage Diameter I think that’s it. Thanks.