I am quite small, and in my experience, yes, it can be difficult to reach when the woman has a bigger booty or bigger thighs. This is especially true for anal sex, because the anus is buried deep between the butt-cheeks, and if the girl has huge round buttocks, it can be very difficult to reach her anus because I am so small. I am not complaining though - there are advantages to being small. Women do tend to be more opened to anal when you are small. I have been with at least a dozen women who had never allowed other men to take them anally because they were too big - and yet they were happy to experiment anally with me, precisely because I am so tiny and non threatening; and if I can't reach the anus because her butt-cheeks are too big, then it is still very pleasurable to to just fuck her deep buttcrack.