pic: Team Fusion's T-Shirt Shooting Robot

[NoodleKnight]

What are you using as the valve? SCH40 PVC is good up to it's pressure rating, which should be printed on the tubes, and I think it's far past 250 psi. The PVC joints are always built stronger than the pvc piping, so as long as you cured/glued the joints correctly, all will be fine.
I always like to put my psi limit depending on the valve, I usually use a normal sprinkler valve, which is good to 120 psi; so I set mine to 100-110 psi and it can shoot stuff far enough for my purposes. If you're using a ball valve, you could go higher, but at that point I'd be scared, lol. I suppose you could make some type of scatter shield for it.
If you're having problems shooting the t-shirt high up into the stands, try cramming the shirt down the barrel, hard. You don't want any air bleeding past the t-shirt.