I would use a standard 6" radius corner for ease of liner installation. 90 degree corners put stress at that point. Your coping stone however, can be set on a 90 degree for a nice finished visual.

If pools are "shifting" as you say, it's best to have a soil engineer check the soil conditions to address and prevent any movement. Perhaps your neighborhood has a high water table? The panels should be set on virgin, stable soil.

Thank you, I appreciate the advice. We are in central Canada and have extremes in weather -40/+40...reason for shifting. The water table isn’t an issue.

I was just having a look at your website. The Alpine 1 image is exactly the shape I’m looking at. The hot tub /waterfall on deep end is beautiful.

Thank you. That 20x40 concrete pool was built in 1979. We renovated it about 8 years. I designed and built the water fall and the spa which became part of the renovation. Giant backyard make-over.