My understanding is that Marks Models kitted Thornburg's Honker Bipe, but it didn't sell, so they came up with a series of semi-scale bipes, SE-5A, Fokker D-7, Pitts, using the same wing design. There were some gliders using that simple thick sheet Jedelski wing also. Thornburg would choose his wood carefully, but that probably goes out the door when you're trying to make a living selling kits.
Ironically, the semi-scale WWII types like the Mustang, P-39 and Spitfire were very light, but the biplanes were heavy because they were based on thick sheet wings.
I was hoping my SE-5A would be OK because of the undercamber, but there was just not enough lift. If I build this again I would use a completely different wing structure and try to keep it simple and light. I think light weight is really important, but especially for smaller types like these. That's why the Mustang was so great...it weighed about half what anyone else's 40 size Mustang weighs.
Please don't go putting a Saito 56 on a WWI bipe this size. It will fly at a scale speed of 400 mph and look totally wrong. Build it light and use a light engine. With a span of 42 inches, this bipe is not even 1/7th scale. People typically use a 50 size four stroke in 1/6th scale, which will generally come out to about 52 to 56 inches in span. In my opinion, even that is overpowered. I used a much less powerful 40 diesel swinging a 13 inch prop on my VK Nieuport 17, which turned it about 7500 rpm, and it flew it beautifully.
The Marks bipe designs are nice and simple, so I would come up with a simpler wing, maybe traditional Jedelsky using light sheet and exposed ribs, and use a 21 to 30 size four stroke. If I went to the trouble of a full built up wing then I would want a more scale like design anyway. The virtue of the Marks designs is their simplicity, yet good looks in the air. I'd keep it that way.
Jim