The ATF is looking into a new way to determine if a firearm is an SBR or a pistol: https://www.atf.gov/rules-and-regula...ilizing-braces
An alleged worksheet to do the determination:
https://i.imgur.com/nKA0DGr.jpg
https://i.imgur.com/YR5dyId.jpg
Note how the use of an LPVO alone would disqualify a firearm from one-handed firing status. The weight thing could also be tough (120 oz is 7.5 lb).