Interesting design. Would like to see a long/ or high use results on this? Wonder if BF Las Vegas has them?....lol
Per the TM, you should stake your end plate/castle nut in two locations, after applying Aeroshell 33ms (TM advises molybdenum disulfide grease, which 33ms is close enough to be used) to the threads of the castle nut and receiver threads, then tightening to 40 +/- 2 INCH/lbs. If you are swapping stock sets alot and not rocking full auto a crap load between swaps, you can get by without staking for the most part IF you don't use 33ms on the threads.
That said, 42 inch pounds is not very much. after lubricating the threads, just tighten until nice and firm, not gorilla tight, then stake. Should have little to no worries, even if on an select fire lower.