Poly straps aren't made to tighten down forever like a TC needs 365 days a year.
I've hauled commercially pulling flatdeck GN trailers up to 32k combined with wheeled equipment and construction materials. Poly ratchet straps have their place but having made a living using them and having owned three different TC years ago I sure wouldn't trust any poly strap for a TC tie down. Maybe for a emergency tie down.
A car/wheeled equipment sitting on a trailer is dead weight at any speed. A TC sitting in a truck bed at speed the overhead acts like a wing constantly lifting the front of the TC. You can feel it in head winds or gusting winds. I would use the approved equipment.
