ive tried all sortsof LER scope options on the Mosin, with pretty weak results.
the B-Square mount is, IMO, a POS and youre going to run into problems unless you modify it or try and bed it in with some JB weld. the mounting screws and set screws are quite poor.
you will need an aftermarket stock or a bubba'd raised comb because the combs of the milsurp mosin stocks are much too low. the scout mounts are much higher profile than a simple weaver base on a tapped receiver, so it further compounds the problem.
honestly if i had to do it all over again i would go with a PU mount and bent bolt. most of the scout mounts on the market are really crap, and by the time you factor in the cost of a good one plus a half-decent scout scope (there are no cheap scout scope solutions) you can get a repro PU mount installed that will also look a lot more professional. or get the type of weaver mount that you mount by drilling/tapping.
at this point after many hours of frustration i have 2 different types of Mosin scout scope mounts sitting in my parts junk bin and my 'hunting' Mosin is wearing its old irons again. another option is just leaving it with iron sights and upgrading it to the Mojo sight systems ghost ring sights, theyre not expensive - $74 for a front/rear set:
at this point i pretty much just

whenever i see any scope mounting solution that involves set screws and aluminum.