FWIW I have had excellent luck with Briley thinwall tubes. My gun had its chokes butchered with hand reamer, off-center. There was not much metal left on one side of the gun's left bore but Briley made it work, on-center. Briley's thin wall tubes pattern well, too.
I would make sure that your gun has already been modified before I went ahead with installing choke tubes. It sounds like your right barrel has about 12/1000 of an inch of choke and your left barrel has about 42/1000. If this is the case, your gun's chokes would seem to be "in the ballpark' for pigeon guns of this gun's period...i.e. "strong IC" and "tighter than Old Nick's hatband FC".
Have you shot the gun, yet? You might be surprised at how well the old girl can be made to perform.
