Thanks for the explanations, I've always been curious about that slow pressure build up. With the solenoid delay off, full pressure into a blind basket following a 3 sec cooling flush goes up from ~10 sec to ~13 sec. Full pressure remains ~4 sec following a backflush as expected.

I'll have to play around with keys115's priming into a blind basket and toferabc's skipping the cooling flush. I've been using some light roast lately that may especially benefit from that.