Question for the NFA gurus:

If I take a 'post ban' lower, put an 11.5" or 14.5" on with the appropriate federal registration and tax stamps as a short barreled rifle, does it still have to comply with the 'no folding stock' and 'no flash suppressor' limitations now that it is an NFA weapon?

Can you 'pre-banize' your 'post ban' in this manner?

Yes, it still has to have post ban features. The only way to eliminate the post ban status would be to ad a RDIAS or Reg. LL. Once you remove the RDIAS or Reg. LL, the gun would be post ban again.

A post-ban will still be post-ban, just a shorter barrel.  ATF says it is still a semi-auto rifle, just shorter.

It is still a post-ban. Here is a quote from Troy from a previous thread. I think he spells it out pretty clear.

Troy is (as always) correct, but to clarify so there's no misunderstanding...

The reason MG's are not subject to the 94AWB is in the definitions.  The 94AWB applies to "semiautomatic" assault rifles.  Thus, as a machinegun is not semiautomatic, the provisions of the 94AWB cannot apply.  The same logic applies to the exception to the 94AWB for AOW's.  They are, by definition, not pistols, rifles, or shotguns.  The 94AWB defines a semiautomatic assault weapon in 4 ways; (1)it can be one of the named models (i.e. "AR15","AUG" etc.), (2) it can be a  rifle with certain features, (3) it can be a semiautomatic pistol with certain features, and (4) it can be a semiautomatic shotgun with certain features.  Since an AOW doesn't fit any of those categories, the 94AWB doesn't apply to them either.