Just because some guys are having problems with the Tangodown grip not fitting well doesn't mean nothing else will fit:
GGG vert. grip, First Samco bipod adapter, FAS2 light mount, SF M952C which uses an ARMS #17, ARMS #19 w/ C. ACOG, Y.H. flip front sight, TDI-Arms light mount & SF X200A. (I know the X200A
doesn't have the battery compartment lid/switch assembly...)
Only the FAS2 was a bit snug feeling but that is a common occurence/complaint with the FAS2 & 3 mounts.