If you are looking for a skinny 18 or 19 year old then perhaps the $150 per hour shops is not the place to be looking.

Occasionally you may find a 23 year old but usually the girls are more mature.

Personally I prefer the more mature girls however I do prefer thin girls even with small tits to larger ladies with larger tits.

But each to their own that's punting.

However what would be nice no matter what your preference is to be polite you could just say you prefer smaller women or you prefer younger girls. Nothing wrong with saying that we all get the message and no one is offended.