I think a 13x4w would work well. In fact, until I flew the 14x4 funfly prop today, I expected to have to cut a half inch off and am not positive yet that some won't be.

One of the selling points for the engine for me was that it provided a wider power band than glow as I've come to personally dislike a screaming 2 stroke glow engine.

The 14x4 prop reduces that screaming noise level towards that of a four stroke engine, not getting there of course but it helps a lot. Of course the prime concern is at what cost to engine temperature.

When I read that the Evo 10cc prop range went through 13x8, I figured 14x4 would not load more than the 13x8 and possibly less. I've got a 13x8 and could test it but doubt I'd like it on the Funfly 3D but it would be interesting to compare loading.

I was surprised by the idle rpm drop from 2500 to 1700 simple by changing the prop. That is a big plus and fortunately enough ground clearance existed to get away with it.