I don't use my quads very often.
I stick to VG for any big shots on a bigger blast, and then use slin pins for everywhere else.
Delta, tris, lats, traps (occasional pec, but I'm not a fan)
In the past I would use slin pins into the rectus femoris, or bigger shots into the lateralis, never had any issues, but the crippling potential of a bad shot deterred me from keeping them in my regular rotation.
On top of that, my deep tissue/PT guy (who works on a bunch of high level pros, including nick walker currently) claims he can feel the scar tissue buildup far more in quads than in other sites. As a guy who already struggles with his quads, I decided to keep that variable to a minimum and only rotate in quads when I have really high injection volume