Here is a site with a lot of photos of the Cap 21.

http://www.toni-clark.com/english/mo...1/cap_foto.htm

Look at the photos. If the cowl bumps were strakes there could be some effect but the cowls are well rounded bumps with no edge to create vortex stuff or anything. The fuselage of the cap is really deep in the front which makes the area less effective.

I don't have the RC experience of Tony but have spent a lot of time evaluating configurations in analysis, wind tunnels and flight test. We did a lot of quick and dirty evaluations in wind tunnels by using a flat plate rather than a fully sectioned part. For instance leading edge strakes like on the F-15 where the gun is located. They can be replaced with a flat plate of the same planform and you will get almost the same data. But these are lifting surfaces. The rounded bump is not.

Based on that I would pretty well say the cowl is not going to act as a lifting surface and the inputs to the NP are pretty well trivial.

I also can't determine why the CG location (within reason) should have any effect on the balloon effect on landing as noted in the site where weight was added to the nose. He is working with approximately the same weight airplane which will require the same angle of attack on landing. There will be some tail trim lift difference but it is actually pretty small. Elevator response will be a little less sensistive but I can't see why that would prevent ballooning due to an aerodynamic factor.

I