Suggest that Maria make a closer comparison

"Well, it can't be as bad as all that," you say slyly. "Maria, why don't you make a closer comparison. I'll bet it's not even that big a difference."

Maria pulls Carson over closer to you. He pretends to be ****, but you notice that he keeps stealing glances at your erection. "I know," Maria says excitedly, and runs off to the closet. She comes back with some sewing tape. Starting with Carson, she uses it to measure his size and estimate his width. "Hm, looks like...almost four inches long, and...three-and-a-half inches across."

You step closer, partly so she can reach you with the measuring tape, but also so that your towering hardon is right next to Carson's pathetic boy-dick. "Okay, let's see...ten inches long, holy shit! And...almost eight inches wide!" They both just stare at your cock for a little while, until Maria says, half-jokingly, "How am I gonna take that thing?" You promise her you'll make it fit.