Definitely USE them! For sure on the long sides where the side uprights/buttress free are, and get the largest ones you can. Use the solid ones, not the ones with holes in them. There is a lot of pressure on those sides that a round pool doesn't have. Plus - it's much easier to level your pool using the patio blocks. If you have to fill under them, though, use stone dust/crushers/screenings, to have a solid base. Do not fill with dirt!

I'd recommend them under all uprights, for round pools too. If there's that much heaving that your pool wall buckles - it's not going to matter if there is a patio block there or not anyway. Only problem I can see with heaving is if you have a deck built above or below the top rail. My pool wintered great - use them for extra insurance!