There is a plethora of designs out there including ARF's that your engine is ideal for. And its getting more all the time with more and more electrics coming along that are ideal for your engine.

First off the Viper Q-500 used as a sport airplane would be perfect for your engine and certainly not be underpowered with it. Most rule book Q-500's fly well with 25's and many use them with that class engine as well as some clubs use 25 spec classes for Ama rulebook racing.

You said you are thinking scale or warbird and I take that to mean WARBIRDS, thats what most really mean when they say it like that and you know what There are a ton of warbirds out there that that engine would be perfect on all you gotta do is look and use a little imagination. I am also guessing when you say build is you are really talking about ARF's which of course you assemble, but hey nothing wrong with that.

Here are to of my little fun airplanes and they have been flying for four to five years now. First is the 'Messed-up-Schmidt' a Modeltech 109 arf sold by hobby people. Your engine would be fine and I intend to reengine this one with a new .OS 35AX (incidently a superb engine and I feel the best in this class) Its currently flying with an old FOX 25.

The Red one is a Modeltech Texan arf and on its third engine. First had a Fox 25 then it wore out an OS 25FX and now it flying wonderfully I might add with an OS 35AX. This still avalible and popular arf is still avalible from hobby people as an arf or Balsa USA as a kit.

These are just two examples of many 25 class airplanes avalible.

John