I just finished doing a hybrid rigid / flex PVC set up for my pool. Did it yesterday, turned on the pump today, no leaks. Thought I would share it because it's a good solution for us soft-siders, which could have too much stress on the pool fittings if totally rigid PVC were used.
1. You'll. notice my only valve is on my pump input, and I have none on the rigid PVC. This is because Lowes did not have union valves in the 1 1/2" size; because of the relatively short lengths of PVC I had, I didn't want both a union and a valve; and I wanted a union for ease of construction and rework. With having a sand filter, I have discovered I only rarely need to shut off the return, anyway; just taking the eyeball out and putting a plug in the pool for those rare times works. If someone wants to adapt this for a cartridge filter set up, or have a longer PVC run on the ground, the might want a valve.
2. The run from the pool to the pump input is totally flex. This is because I was just going to go with flex PVC, and only decided on a hybrid because I couldn't seem to keep the length that was mostly in the air, from the filter output, to the pool, from leaking. Since this was on the ground, with having an in the pool skimmer thats hookup is at the pool bottom, I had no problem with that one. Someone with a higher skimmer output might want to put some rigid where I have flex.
3. The filter / pump connection is flex. Arbitrary; I set it up flex a couple of years ago, and it wasn't leaking, I didn't change it.