naturally some people will fall outside our standards but let's not jerk circles about how disgusted we are or repeat any /fit/ talking points about morality. we're all anons here, we have nothing to prove. You don't get a trophy for turning down a big girl, any more than another guy would get a trophy for fucking her. (apart from getting to fuck, of course.)
So, let's narrow it down. You're walking down the street and a person in the age/gender range you're interested in is walking the other way. how big before you no longer turn and YOWZA?
I bet most guys have a size where you'd go for it, maybe even chase her a little, but be embarrassed if your friends found out. pic related.