boyfriends comment

I was discussing ways to enhance my partner and i's sex life. I started off flirtatiously mentioning a few positions, upon mentioning a doggy style idea he (not so smoothly) told me my butt was too big for such a position to be effective.
I'm not the biggest girl but i am bigger then my partner both a few kilos heavier and a few centermeters higher. Nothing major. But apart from shaking my confidence and self esteem it got me wondering if this is true? Does my ass effect his pleasure? Do skinny (like very skinny) girls have advantages that us curvier ladies don't?

ta,

Jay