The builders may want to copy the long thread on frame sizes from the "old" Lefever forum. If all information submitted was correct, the XX frame was of more than one firing pin separation dimension. As we all know, firing pin separation is what makes a frame suitable for whatever gauges. It is the dimension that the rest of the frame is built around. The size of the breech balls is secondary to pin separation. Firing pin separation can and should be sufficient for 16 gauge use, and can be without being too bulky for 20 and 28 gauge use. Using Parkers and Lefevers for an example, 16 gauge guns were commonly made with firing pin separation of as little as one inch. However, Parker made at least one ten gauge gun on a frame with firing pin separation of 1 1/16" firing pin separation, so it may be possible to make a 16 with separation of less than one inch. In my opinion, the 26" barrel option could be canned for a 30" option. A.H.Fox for one example, commonly used cut 28" barrel sets to fill orders for 26" open bored guns when finished 26" barrel sets were in short supply. There shouldn't be a need to stockpile the recently less than popular 26" barrel sets for the new Lefever when existing 28" sets can be cut to 26" for those who prefer them. Long chokes should insure that at least an improved cylinder and modified will remain in a barrel set cut 2 inches.