Yeah... Um... NO. He's going to lead her on and if they hook up, she's going to be severely disappointed and he's going to take a huge emotional beating, thinking that the only way to satisfy a girl is to be hung like a horse (like you.) When the ultimate truth would be that her disappointment is that he lied, not the size of his dick.
Do him a favor and turn him down. (And not just because then he can use that video EVERYWHERE to show off your dick, claiming it as his own.)