Lowvoltage,
I have, as has airbusdrvr, built both the Venture and the Flyin'King.
The FK is powered by a Saito .91. It was built as a taildragger with no modifications from Bruce's design. The .91 is more than ample power for it. With flaps, on thick grass, the takeoff roll is a few feet and rarely is a power setting above half-throttle used while the plane is in the air.
Both of my ventures have been powered by Saito .82s. It is a nice match to the airframe with power above half-throttle being required for takeoff and aerobatics only. It does not have unlimited vertical with this engine. However, the engines are run on 15% nitromethane fuel and are turning wooden ProZinger propellers. A lot of people use higher-nitro fuel in their Saitos and APC propellers seem to be popular. Personally, I am a little too attached to my fingers to use a plastic or composite prop. And, I like the looks of wood. Perhaps a penalty is paid in performance.
Both planes operate from thick grass and were built as drawn. No modifications to gear position.
With the Venture, when operating from grass, propellers greater than 13" in diameter tend to be problematic due to ground clearance problems. I use a 14" on the FK with no clearance problems at all.
Enjoy your machines.