In the old days, Safariland made some upside down holsters, but the method of retention was a little different. There were no springs, just a piece of elastic across the front of the holster. They made them for J-frames, K-frames, and various Colts, which included 4" barreled models. I carried a Model 67 in one for quite a while. It was quite comfortable, and pretty secure. Your revolver wouldn't even come close to falling out. Old Safariland leather was good stuff, and I wished they still made some of the models that were made back then, but alas, I guess there's not much of a market for that kind of stuff in this day and time. I also used the Bianchi for a J-frame back then, but I've never seen a Berns & Martin holster in person.