To answer the other part of your question about the above ground pool decking. I'll tell you about my pool. I currently have a 24 ft AG pool with a deck built approximately a third of the way around the perimeter of the pool. The edge of my deck aligns with the curve of my pool, but the decking boards do NOT sit on the top rail of the pool. There is a gap between the top rail and the underneath side of the decking boards. I lay 2 x 4s on the top rail which fills in the space and then these 2 x4s are screwed to the decking boards. This provides support so that if you are stepping on the edge of the decking board, the decking boards don't sag. Plus, in the winter, the 2 x 4s are removed so that if you want to put on a winter cover, you can easily do so. (I don't use a winter cover anymore.) I'll see if I can find a picture of my pool and deck so you can better see what I am talking about.

We are currently in the process of looking to buy a new AG pool but we're going with a 27 ft AG with 54 inch walls this time. This will mean that we'll have to replace the deck since the arc of the bigger pool will not match the existing deck.

(I can make the correction in your thread title for you.)