I think the reason you don't see many 3D aircraft in that small of a size is just because it's harder to do 3D the smaller the plane gets. Presentation is not the only reason the Pro's are using 40% planes, it's becuase they are easier to fly. Partly because it's easier to see what they are doing and partly because the airflow is better managed and more "realistic" (I tried to think of a better word - there's nothing realistic about a hover). It's like those tiny electric park flier biplanes, they are just really twitchy and very difficult to fly and do 3D with.

If your just getting into 3D I'd look for the biggest plane that reasonably fits into your budget... Something at least 60 size. Aeroworks makes a nice 60/90 size edge 540 ARF for example. Or maybe a H9 Funtana. A lot of people like the U-Can-Do-3D. I own one of these and am not happy with the build quality. Excellent flying plane, buy you almost need to take it apart and put it back together again to make it work.

If your set on doing a small 3d plane, maybe build one yourself out of foam? I dunno. I imagine a plane for an engine that small should have no more than 35"- 40" of wingspan (2-3 lbs at the most)

I know I'm not answering you question, but I hope it helps anyhoo.