Paul, a couple of the items on your Kitfox speed mods. wish list have been done.

The strut to wing attach points for instance. Murle Williams had them on his Model 5 years ago. I have had a set of the same plastic fairings sitting in my hangar since before I first flew my Model 4 back in 2003. I just never painted them and installed them. They do look nice though.

Also the landing gear (Grove) have been faired into the fuselage on a couple Arizona Kitfoxs going back to Murle Williams 1997 model 5 Grand Champion. Phil Laker I think did that mod to his Vixen also.

All those mods should be effective for increasing speed. We just don't know exactly how effective. It would add build time to the aircraft but for some that isn't a concern. Weight has to be factored in also but most of the mods you mentioned can be, and some have been done, with careful attention to minimizing weight gain.

It is always nice to pick up a few mph to your cruise speed and or reduce your power setting and leave more fuel in your tanks for the same cruise speeds.