I cannot see by what engineering or gunmaking criteria a V sprung sidelock or boxlock can compare to a coil sprung Beretta 626 which is owner serviceable, has parts that drop in without handfitting. A 626 even has intercepting bents on its hammers, something few boxlocks have.

With a budget of 5000 USD you can get a fine used 626, restock it to personal dimensions, remove the bottom rib to lighten it, (if you really need that kind of lightness), and never worry about its strength and ability to digest modern loads. When the time comes to rebarrel its monobloc barrels can be renewed and reblacked in a couple of weeks at a reasonable cost.