Depending on where you live, I WOULD in fact use patio block on the curved sides of an oval pool. We did at the suggestion of the folks here and I believe it was the smart way to go. One would think that the longer the pool sides are, the better prepared support system you would want - pressure is different on the long sides than the curved, but good support all around is peace of mind. Round pools are much different as far as pressure and structure. Ours is buttress free as well.