rustle Yes, I will have to admit to flying GA7s with Cabair
It operates a total of about 12 x GA7s, of which roughly half (I believe?) have factory fitted unfeathering accumulators (AC).
I must disagree, when you say that those without ACs need a higher airspeed to unfeather a prop. In my limited experience (only a PPL & not too good on the techie stuff!) an engine without an AC, will not (& should not) unfeather itself, however much you increase the airspeed. It just sits there fully feathered. I have actually tried this in a GA7, just to see what would happen, & the answer was precisely nothing!
In a GA7 with ACs, if you are bumbling along, with 1 engine closed down, at just above blue-line speed of 85K, & do a restart, as you move the prop lever to fully forward, you can actually see the blades twisting from feather to fully fine. BUT, at 85k, the prop will not rotate AT ALL. As you put the nose down & approach 100k, it starts windmilling, & then starts up.
For a GA7 with no ACs, then when using the electric starter motor, after a close down in flight, during the first turn or 2 of the prop, you can see the blades unfeathering.