Don't be afraid the units that lay down don't work, they surely do. Just like x-mas trees and natural cover it will still attract and hold fish.
The rule we discovered was it needs to stand up on it's own in the driveway inj a brisk wind. If so, the balance is correct. PVC is heavy and sinks on it's own so watch the top side.
Height is directly affected by base diameter far more than actual weight of cement/container.