I'll be generous to myself and describe myself as very average build, size and proportions. Notwithstanding that I've had nice remarks about various aspects of my physique several times and my "big" cock once. Given these comments are from someone I just gave a £100+ to, I take them with a huge pinch of salt.
As to cock size, humans have evolved over millions of years with cocks needing to fit in fannies to procreate so most cocks should fit in most fannies I reckon. Lastly, no matter how big, small, wide, thick you are I guarantee she's seen one bigger and smaller.