thanks for input and that's what I'm planning to do as well. Do you also crack the spa suction valve halfway or part of the way?I have Aqualink with spill-over spa and haven't used the mode that switches between Spa and Pool every half hour. Seems like Rube Goldberg-ish wear and tear to me: a lot of valve and pump switching (mine shuts down while changing modes). Cracking the spa return a bit has worked great even with the pump running 1200 rpm and ~38 gpm. When it's balanced the spill-over stops but the spa remains full. With freeze protect @1800 rpm as already mentioned the spill-over trickles, which is nice. So I can just set this up in November and go back to normal in April. nb: I do winterize spa bubbler pump and deck jets with my little shop compressor.
I'm concerned about my sheer decents as well. When I open the spa return partially the flow out of sheer decents drops to almost nothing as they are not on a seperate pump. so I have to raise my pump RPM to about 3000 or so to keep what I'd consider enough flow for them. I'll have ice build up for sure on my pool where where the decents are but I guess that's the least of my worries.