The "psi " thing is only applicable if you use "black poly pipe" or mid-grade HDPE. Big hoop users would use black poly, I used them to teach beginners. You sound like you are advancing a lot and ready to go beyond the old black poly.Polypropylene is popular now but its light and exactly the same flimsy plastic used in cheap hoops from wallmart. its funny how people stampede to the newest thing. My hoops are much denser, more resilient and last much longer. They are made of hdpe as well, but its a type that extruded in a way that give it near perfect "memory" or "spring back". its more expensive but way better. its pipe not tubing so the diminsions are nominal , not exact. (Most poly is pipe , not tubing as well) comes in 1/2, 5/8, 3/4 and up.

Here's a couple of  formulas for appropriate hoop size: 1. what hoop can you comfortably hoop on your ankle while lifting your leg? 2. measure from armpit or inside shoulder to opposite wrist to get a medium - advanced hoop size. and an expert hoop is measured from the sternum to middle of the thumb knuckle. this allows you to do virtually all mini tricks , isolation tricks and extra-orbitals then transition to the body smoothly- I strive for this because i think it looks awkward to switch hoop sizes during an act. Beginners should use a hoop that goes up to belly button or from tip of fingers to outside of opposite shoulder. Begginers who are having trouble should just use the biggest hoop they can fit in their car. these are good to have anyway, you get the hang of it soon, then use the hoop for tandem hoopin!

Hoopiness happens when happily hoopin!