im a true 7.2 by 5.8 inches (about the same size as a sky+ remote -check out my photos) and i cannot have sex very often with my girlfriend because it hurts her. she complains of a knocking sensation in her tummy and it often puts her off sex for a week or so- she sometimes bleeds. we dont really do it doggy or with her legs over her head - shame as i like these positions and like to do it hard. (i do weigh over 15 stone tho ,and no im not fat, i love the gym, but this could also be a factor of pain. my ex girlfriend was the same too -big no no to doggy due to pain. i bet u bigger guys must be in the same situation as me if not worse. i reakon not to big but not too small.