The problem in looking at Rutan's designs is finding an airplane to compare them to that is the same except for only the tractor-pusher change. They are beautifully designed airplanes but since so much changes from something like a Piper Cub (insert an appropriate airplane name) you can't just isolate the engine location effects.

Having a Swedish fighter that went faster than what was calculated just means that the original calculations were wrong, not that the pusher engine was better, etc. Remember those were times when the state of the art was pretty backward compared to today's knowledge base.

If a model like Dick's twin boom airplanes were made with two fuselages, one tractor and the other pusher, and some tests made with respect to speed or fuel flow or endurance or ??? then a reasonable conclusion could be made. I will accept Dick's analysis on this since he has designed and analyzed the configurations and has enough experience to evaluate the results.

Do keep in mind that things like the prop working in messed up airflow behind the fuselage and wing can have impact on whether or not the design is acceptable. You can get destructive vibrations built up as a result. Again the prop working in clean air at the nose is the best place for all around work, maneuvering, high load factor, and the like. Having a surface of any kind, whether prop or wing, in clean air is nicer.