RE: Picco 45 DF
My Nelson 40 hits 30,000 in the air with a 6.75" x 7 prop. I don't recall trying less diameter than that...since the hand launches were pretty wimpy for the first 20 feet after leaving my hand. IIRC the launch rpm has to be no higher than 22,000 on that prop because of no inflight mixture control. So, 3 pounds of thrust to launch a 4 pound model.