The rpm of the props are 3750 rpm. The gear ratio is 9.8:1. I chose the 22 inch diameter prop because I wanted to swing as large a diameter prop as I could to maximize propeller efficiency, and I chose 18 inches of pitch because I was trading off reduced propeller efficiency at low speeds versus straight line flight speed.

Based on my initial flight tests it looks like the 22X18 prop is working well, but there are fewer problems at low speeds than I anticipated, which is probably due to the fact that the front prop speeds the air up before it enters the blades of the second prop, so even if the front prop blades are stalled, the rear prop blades aren't. Based on this I think I could increase pitch up to 20 inches and beyond, and still not have problems at low speed.

Comparing system weights isn't straight forward because I'm removing the stock Hacker gearcase, and the stock spinner, and replacing them with a new spinner/gearcase that's integrated into a single assembly, and then I'm adding a second prop.

However, what I can say is that the Integral with the complete contra rotating system and the same flight pack, came out two ounces heavier than my old Integral with the stock Hacker C50-14XL, and a single 21X14 APC prop.