The confusion is "NFA" which to me means "
National Firearms Act", not "New Frontier Armory".
So, yes, using my defintion of "NFA" when I mentioned a two stamp gun I was talking about adding a supressor -- one stamp for the short barreled rifle (SBR) or machine gun (MG) (the "NFA lower" -- my defiinition) and one stamp for the supressor, which is why I pointed to redtazdog's 4.5" barrels.
So OP, ignore my suggestions, they're illegal for a "New Frontier Armory" lower, but not for a lower that's goverened by the "National Firearms Act".
O2