I don't cover my pool - period.
I shock, drop the level - why? - I really don't know, because rain and snow just fills it again!
Your ice theory is good Sevver, however, if the pool freezes solid, theory becomes nul and void. Up here, pools freeze solid - AG pools anyways.
Here's what really happens when they freeze - ice will expand - no doubt about that, however, it will expand in the direction of least resistance first - meaning up/down.
When my pool frezzes partially (1 foot), there is a gap between the wall and ice about 1/4" thick through which I can force water up if pushing on the ice, likely due to friction. If it freezes solid, the gap is still there, however, no water - makes sense - it's frozen solid.
If you put a plastic water bottle standing up in the freezer with 2" air at the top, the bottle will not stretch around the perimeter, however, the 2" air gap on top gets reduced to a smaller space.
Pillows are supposed to keep the water off your cover by lifting it, they are not in there to absorb expansion, if they were, they would have to be submersed from bottom of pool to surface of pool, floating them on top does nothing to help absorb expansion. Lifting the cover and running the water off is supposed to alleviate streeses to the structure on AG pools (like walls pulling in - the #1 cause of Pool collapse in Canada), and keep covers from pulling out from under the weights on IG pools and sinking into the pool. However, if you place a couple of pillows on your pool, it will only make the water move to a different location on the cover, so the pillows really don't do anything.
The only way to remove water completely off the cover would be to build a roof support structure under the cover similar to a pool greenhouse - I don't think anyone would want to go through that trouble.
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