That’ll only be about 45psi in head pressure. So shouldn’t effect your draw rate, imo.
But I agree that ds’ing straight mix might not work very quickly on that surface.
Xjet from the lift might not get you full roof-strength mix, but I bet it’d be close enough for that substrate. I’m guessing around 2.5-3% will melt that growth right off the tower. Just my uneducated guess.
