Memory foam doesn’t need to be a custom order. Just cut to fit.
Freezing? Ive never heard that but I suppose I believe you. However does it make a difference in your decision? There is nothing reasonable you can do to prevent that (if it’s actually a thing) that is remotely as cheap as losing, say $50 worth of “expected use” out of it.
Or bring it inside in the winter and keep it cozy by the fire until the robins are gettin worms again in the front yard.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold