It wouldn't do any good.

"You know it wouldn't matter at this point," you tell Jill as she pushes her cock into your butt. Her swollen belly presses into your back and her swollen balls squeeze between your legs before she starts fucking you.
"You're right," she quips. "Nobody wants to deny themselves pleasure. Your butt feels great slapping against my crotch the way it is now. I should make you wear my clothes all day, every day!"
"Not like your bras or shirts would fit me, since they are all stretched out. Oh wait you didn't bring any bras, did you?"
She wraps her tits around your torso so you can play with them...or to get a tighter grip on you.
"I have plenty of fun things in the bags I brought with me," she says. "Here, hold these as if they were yours."
Jill pulls her tits so they sit on your chest and then lets you hold the heavy flesh orbs. Next thing you see is Jill reaching to grab her thin yellow shirt, which she pulls over your head. She then pulls it over her tits.
"Now let go and put your arms through the holes," she instructs as she holds her tits from the outside of the shirt. After you obey, she lets go and her tits rest heavily in the shirt.
"Wow I can feel the weight of them," you tell her.
"That's because you are wearing the shirt which supports them. It's nice that they are big enough for the both of us, hmm? I don't mind not carrying the weight around."
Jill cups her tits as if they were yours as she resumes screwing you. You can feel them bouncing against your chest. You run your hands over the nipples.
"Oh, so sexy. Here's something for your trouble," Jill whispers as she cums. You see her grasping her own tits hard as she gets another load out of her system. Before she finishes, she withdraws and the ropes fly from her dick and stick to your cheeks. Even though you felt full, she still manages to coat your cheeks rather well too.
"A bonus?" You feel at the cum coating your ass has gotten.
"Yes! Now pull those up," Jill says as she tugs on the waistband of the shorts. You help her pull them up. They feel as they did before, just way more slippery and wet. When she grabs your butt, it makes wet sounds.
"Sounds good," you declare.
"Very good," Jill agrees. You shake your butt a little as she kneads your cheeks.
"But what about underwear? Unless you don't want me soiling your panties," you joke, sure she doesn't wear them.
"Oh, you want them now? I thought I would have to convince you to wear them. I'll grab some right now!"
She pulls your shirt off to free her tits, then goes over to her bags. She pulls out red panties and shows you them. Then Jill puts them on. The waistband sits high on her hips. Her softening cock sticks out of the waistband, so she folds it over and tucks her cockhead back inside the front.
"Do you like these?" She turns around so you can see the panties cover only the top half of her ass, and below that is a strip that barely covers her crack. "If you don't, I have others I can show you."
"They look great," you tell her, and they do. You don't think before you say it though. You try to distract her. "The front view is better." She turns back facing you. She enjoys the attention, you deduce, as you watch her cock grow hard again. Despite the unnatural length, and the fact that panties are built without consideration for length, the panties survive.
"Ahh," she sighs conceitedly, hands on her hips. "I have a helluva wedgie now."
With that, she strokes her cock near the end where the panties still cover her. Jill eyes you intently. She winks at you.
"Those are going to be all stretched out," you say.
"Nonsense. They are very stretchy. You don't mind if I make a deposit in these, do you?" You see the panties jump over her cockhead numerous times as a wet spot forms and grows. Some shoots through the material and runs down the front. When she is finished, cum is running down her legs. "Good," she answers her own question. She peels them off. "Here you go." She holds them out for you to take. This is why you shouldn't have said anything.
Shirking the shorts which you havn't even zipped up yet, you pull the wet silky panties up and around your waist. Jill helps you by pulling the waistband high into place over your waistline.
"Oops. Looks like your butt is so big the bottom part is a thong on you too!" You can feel it bunched up around your hole. "How are they? You like the present I left you?" She feels around front to her cummy mess sitting against your crotch. She didn't stretch them out, you realize.
"Yes! You want a go in my butt before I put the shorts on?" You wiggle your panty-clad cheeks at her.
"Sure! You want another load in there too, right?" she asks as she pulls the bunched up garment aside and enters you once again. "Or would you prefer I bust a nut on your ass?"
"Doesn't matter, either is fine. I notice your balls are looking lighter."
"They are still huge! But they are easier to move around. I like this silky feeling on my crotch." She bottoms out and grinds against you.
"You could just wear your own," you suggest.
"They look way better on you!"
"I have to disagree. They looked very nice on you," you insist.
"I don't doubt that. They look better on you, though, especially..." she withdraws and starts blasting ropes onto your butt again, "...when you wear my cum with them!"
She blasts another full load onto your butt. After she finishes, you don't even smear the ropes around to evenly coat yourself. She did manage to hit only your exposed flesh. That won't do! You reach down and grab her cock where it rests against your leg.
"Hope you are still horny," you say.
"Why?"
"You forgot to get the back!"
You stick her cock into your crack, then pull the panties over it. Her cock nestles into your crack, and the head catches in the waistband on top. You move so her cock slides along your crack.
"Oh, a pantyjob? That's really hot! I'm gonna fill up your panties!"
"Your panties," you correct her.
"Oh no, they are yours too now! You can wear anything of mine whenever you want! I'll even give you first dibs! I just get to put something in them before you use them," she giggles.
"Like what?"
"This!" She cums. Some of it shoots through the thin material, but most of it runs down the inside. You aim it so it gets everywhere. You can feel some of it collect in your crack. Then you pull her cock out and snap the material back in place.
"It's very wet," you announce.
"Yes, it is," Jill tells you proudly.
Then, you pull the shorts on and zip them up.