Toying with doing an integral for a Sub2000 9mm.
7" barrel, 10" can.

if it's integral, pinned and welded to the barrel, what length goes on the F1 ?

This is not to nitpick, but to make it clear. What you're doing isn't an integral, but a dedicated, right? You're just welding/pinning a silencer to a barrel, to avoid an SBR stamp, correct? In this case, just file for the actual silencer's length. In the case of a true integral, the tube would usually reflex all the way back over the barrel. For this, you'd need to include the entire length.