No worries, story of my life really.
Anyways, the average penis is 14 -16cm long when erect, and a circumference or girth (thickness) of 12-13cm.
I'm sure you mean the length, so most guys should be okay in that department.
Got these figures off a UK site, I presume they are for white guys, so black guys might be in trouble.
There are these donut type rings you can put on the penis to prevent deep penetration, specifically for ladies that have very sensitive cervixes see link:
http://www.comeclose.co.uk/
Might be useful for the well endowed client.
Hope you're enjoying Ireland Cocoa, xx.