Barrel thickness will not be an issue. My suggestion is get it as low as possible on the barrel. I sent him a weaver rail to put on mine and he did a great job but I now see that I should have used a lower rail.
Well, I just replaced my red dot sight with a traditional cross hair scope and now realize I needed the extra height from the base to get clearance above the hammer.
Deadbuck, if you need to raise the comb height look up "Accu-riser" it is a rubber comb that attaches like a recoil pad with two screws. They also have ones that strap on. I don't know how to post a link or I would. Going to use one next time I need to raise a comb, but will use threaded inserts countersunk into stock and machine screws so I could remove and install it if needed for dual purpose guns.