I wouldn't doubt that the dovetail geometry could be improved. Some revolvers don't even have a problem with them walking out so, they must be doing something almost right. when I finally resorted to j&b weld, I laid some in the tightened dovetail slot, tapped the seat in and then put a bit around the edges. It's visible if you look for it. fortunately, it's dark colored and not too ugly. In any case, It beats having the lever catch disappear into the grass.
the book will google up if you put in "Percussion Pistols and Revolvers. Amazon and barnes and noble have it as do a bunch of other internet sites. If you can figure out the cost of shipping, you may be able to find a bargain.
I don't know about tight vs loose arbors (fit with the barrel channel) but all mine seem to slide in with a close fit.
One thing I've learned after writing for Guns and American Handgunner for a number of years is that I have zero influence on any of the gun companies or distributors. They do what they want to and I can't figure them out much less influence them. right now, we are in a screwed situation as the revolvers, percussion caps and no doubt other periperals are getting hard to find. The entire shooting industry is sensitive to things like protracted wars, looming economic downturns and such. A lot of the key metals are going into military ammunition and the commercial concerns are directing their supplies into the highest demand products. As far as I can tell, Remington has stopped making percussion caps and the centerfire primers and brass cases are scarce too.