Oh, I agree... I think above ground pools are way minimized compared to in-ground pools. The depth doesn't matter much, since it isn't like you see multiple returns in the deep-end alone. And average wise, it still is the same amount of water for a large above ground pool and a "normal" in-ground pool. Of course extremely large in-ground pools are much bigger, but realistically water volume is water volume...

I have been looking at pool system hydraulic designs for a few months now and it is just amazing that water turnover and circulation is taken way more seriously for in-ground pools...

I would have to imagine an above ground at 20k gallons would need a mimimum of the same type of plumbing for a comparable in-ground to be just as effective. Sure, the majority of the above-ground industry gets by with a single return and a single skimmer. But, "accepted" is far from "ideal".

That is why I am going with a dual main drain, at least two returns and 1 skimmer. I don't have trees above the pool, so a single skimmer should do just fine. The main drains are ideal to reduce the amount of time vacuuming or using an auxillary pool cleaner as well as affording for better overall "mixing". Multiple returns just make sense for the size of the pool (27ft x 54").

I mean in regards to equipment, the same argument goes for the pumps. I understand why in-ground pumps need to pull a head of water, but even for say a 1.5hp pump, the in-ground variants at the same HP rating have way more flow. Again, outside of the head of water, it doesn't make sense. It does when you figure in extra water features, multiple returns, etc, etc... So, does that mean with my setup, I should be looking at in-ground pumps and I have a way "undersized" pump at this point? (for reference I have a Pentair Dynamo 1.5hp 2-speed pump)