I use 1.5" pins in my quads most of the time. Sometimes I bury the needle and sometimes I leave a little sticking out. I agree with post above that leaving some of the needle sticking out decreases the stability of the injection so if you aren't going to put it all in then it is better to use a 1" pin. I am just too cheap to get new pins for quads, delts, bis, tris, and glutes so I am using 1.5" on all of them until I run out.
giantset