I think probably you can answer that question better than any of us.. Only you can feel how much fat you got on your ass.. I know for me 1 inch would be borderline and I would be risking giving myself an absess which could turn into an infection. If I were you I would go for the 23g 1 1/2 pin just to be safe.. It's not going to hurt more, for me the only pain is the initial puncture.