Re: VLTOR VIS and Unimount
I have 2 guns built on VIS uppers. One has an aimpoint that does not bridge the joint, the other has a NF in a larue that does bridge the joint. Although the VIS is advertised as a monolithic upper and VLTOR claims you can treat it as such, I occasionally see lube seeping from the joint area. The NF equipped gun has always held zero, but it's basically a range toy and has not seen extreme hard use. Both uppers are solid; there is no discernable slop whatsoever.
I think you'd be ok bridging the joint with the NF mount. If you'll be beating the crap out of the gun regularly, I'd call VLTOR and get their opinion.