Evidently you can’t get the ratchet or mechanism tight enough?
Does the cover have loops for bungees?
If yes, and Assuming you roll the cover from back to front to remove, as you install the cover (rolling front to back), hook bungees from the loops to the lift cradle. Likely need to do both sides so it is “pulling” the same on both sides.
Suction cups could work too, but would be annoying to watch them fail from inside the house during a rainy windstorm...