I don't see any reason why you should mention it, she might be disappointed, but if you tell her before you even meet her you run the risk of her blowing you off.
Depends what you're looking for; a quick lay or something serious. If she blows you off then she wasn't worth the effort if it's the latter.
In truth, I've never warned and it has not been a problem. I've got 5x4 so you're at least half an inch bigger in girth.
I use a trick to turn a worm into a dragon. :wizard:
Start with the heavy petting, fingering, etc. with your pants still on. Keep it dark. Then go down on her. When you feel she's wet, insert your pinky into the vagina like a penis and keep it there, stroking in and out just like a penis. The vaginal entry will shrink to fit your pinky (or other finger if they're slim). Try not to make her orgasm but get her close. Then when she's reached the plateau phase, drop the drawers, slip on a condom, and enter her. Because the vagina has adjusted to the girth of the pinky, your dick will feel much bigger and give her great friction. Remember that girth makes a big deal in how things work. Keep your pelvis in close, grinding your pubis against hers to keep the clitoral stimulation going. Use one hand to steady yourself, and another to stimulate her clitoris intermittently. Go down on her again if need be, reinserting the pinky to keep things tight. When she plateaus again, this go as deep as you can and do lots of shallow quick thrusts with your head (as it's the widest part of your particular cock) while using your hand on her clitoris. She should, if things go right, arch her back and have the ride of her life.
Do it right and by the time it's over she won't give a damn what's between your legs so long as you have two balls.
Good luck dude and let us know how it goes :smile:.