I’ve run both a Stark grip and a Fab Defense.
The Stark is a bit wider and hangs down lower than the Fab Defense. Larger hands would prefer the Stark and I run several of those on other setups like my Scorpion Evo & PAK 9.
But I changed it to a Nightstrike Diamondback, and I think I like it better.
if you grip with your thumb over top of the handguard then something like a Magpul AFG or Fab Defense works, but I find the sub is a bit short for that style grip and I run a light/laser combo so my grip is further back. So I keep my left hand under the grip with my elbow tucked close.