Well I have one, along with the AML. The plan was to mount it on a .36 cal GM barrel I have for my Renegade but that rifle has a bit wider stock at the panels so I'll have to remove a bit of wood to make the base fit. ( it might be the 1'' barrel that causes that) I'm not afraid to do so but I have a few other projects on the list before I get to that one.
I just tried a fit to my cabelas .54, my custom Kentucky .40 and my son's Traditions .50 and the base will fit on each, useing one tang screw and I'll hafta drill and tap the second hole in the tang. I might just mount it on the 40 and use it for "light bench".?
More important info for you I think, is that the 57 sits lower on the frame because it sits so far back, looking through the peep while it's on the .54 I can see my current installed rear site and the front blade and line up as if it wasn't there, in other words the current height of the front blade is/would be fine,,it's .380 high. same thing on the other two guns with a front blade height of .345 and .360,,,so I don't think the extra height of .584 or .852 is needed at least for the application I need. I do a bunch of rendezvous shooting and my local BP gunsmith has installed a bunch of these and supports the AML standard size.
Well I hope that's more info for ya,,Good luck, sure is good to hear ya dug out the .40 AND found a group to shoot with, that's alway's fun