"He who marches out of step hears another drum." ~ Ken Kesey
for the cost of a real stretching setup, you'd be better off just sending them out to somebody for re-stretch. Maxie's suggestion of a roller frame would certainly work tho...not sure what size frames you have, but 23x31 frames, remeshed with 'S'-mesh (160/48) generally cost us around $20 or so, certainly wouldn't be worth my time...
Up to last year, I was getting screens re-stretched, but with the switch to dimensional weight shipping charges, it became less practical. I have a pile now, and if someone local doesn't pop up, I have a feeling that these will become worth their weight in scrap aluminum prices.