Use an inch and plug it all the way. Feels way better. I used to sketch out and not go deep enough but the deeper the better. You can't feel shit if you use an inch or longer.
1.5" just freaks me out. I use 1" for everything. Thankfully my rumpus doesn't have much booty fat so 1" is perfect for glutes too. I hit delts, glutes, bis and tris... I hit quads too but every few months it makes me so nervous and twitchy that I stop. I can never get used to it.