I wouldn't mind one in 38/357 or 44 mag/spec over a 20ga or even a 28. Or a 357 mag or 44 mag o/u?
If the frame could take it imagine a 45/70 over a 16ga or 12ga. Lots of cool options one can dream up.
Think they are 3/8 grooves though so would want it drilled and tapped.
