Thanks
Ahhh, wow, I don't envy the Mickey Head. Thankfully I am only after a rectangle and would go for an off the shelf but....
1) The space I've got to put it in means the OTS ones I've seen are either just too big or too small
2) I want something a bit more heavy duty than an inflatable or framed one
3) I don't want to pay the premium (Yea, yea, I know, fools errand) for a rigid above ground unit
4) I'm good with my hands and an experienced DIYer including plumbing, wiring, building, plastering... etc
5) I want a deeper pool, but without it coming up too high so I can deck it out of season.
6) I'm planning to integrate a firepit / solar hybrid heater
7) I get to say "I made that"
My current plan is a 1/3 submerged concrete block build (blocks layed flat), optionally rendered inside, then paint with an epoxy or rubber paint. I'll then clad the outside to cover pipes and provide outdoor lighting with a retractable deck panel over the top. My only outstanding query is if I could use aerated concrete blocks to improve the thermal stability of the water or whether they won't provide enough strength.