I've never had tarptents turn down a request. You might try emailing them. They're not in it for the money so I really enjoy their helpful nature and sincere appreciation of their customers.
I've never had REI deny a return even 2 years later on a backpack…
Good luck and remember most of this stuff isn't very durable so be careful testing things you don't own.
Another option is always make your own since you sound like you want custom gear at the Walmart price. (Who doesn't?)
I've built about 10 shelters out of one old ripped up spinnaker sail that did not make it through the nationals S2 7.9 races one year. It is 0.8oz/yd spinnaker fabric for pennies on the dollar versus new fabric. Reuse recycle reduce all that jazz. The spinnaker sails I've purchased watching for the sponsored guys to rip them up will last me and everyone I know a lifetime and I make a couple hundred bucks selling my shelters versus the $20/pop most "professional builders" can rake in.
I worked in a sail loft for years and a lot of the guys are sponsored and will take practically nothing for a $2,000 worth of material $8,000 spinnaker. I mean it has to be pretty well shredded but every once in a while I find a dirt cheap steal of a deal. Typically these sails are just used as patching material in the future anyway for guys like me that name their spinnaker "patchy Mcgee" lol
Prototypes are easily made out of polypropylene cloth or spun bound olefin from cconstruction sites.
Just something to think about in future since you seem like a diy guy to me!