For years, no make that decades, the scientific community and fly fishers with a scientific bent have tried to figure out a few things as far as trout and the connection to what they see, how they see it, do they see color, do they smell, etc. It's as if these people 'know for a fact' that they can determine any of the above through some test or another. The scientific basis is always - The fish do something as we determine they perceive it. In other words, trout see something the way we say because that's how we believe they see it. So the scientists establish the end result then determine how the trout reaction fits into the desired result. Gee, that almost sounds like 'manmade global warming' theories. But I digress. Decades ago I was given several boxes of hooks that were painted white. The guy told me that helps reflect light better and keeps the color of the body, especially dubbed fur, closer to the original color. I also read numerous times about white and silver mylar for underbodies.
You want an experiment, here's one that you can rest assured will be accurate IF you are very observant: Take 10 flies tied regularly and 10 of the same pattern tied with some uv body material. Go to a bridge that spans some good trout water. Just drop the 20 flies and see which ones are taken by the the trout. I say this is a good test but you have to be able to differentiate the uv from the regular. Not that easy. You may need a friend to observe with another set of eyes. One time on the Hale's Eddy Bridge, it spans the west branch Delaware, I accidentally dropped some flies. They were quickly taken by some trout. Interesting because when you do this the flies have absolutely no drag. Anyway, I was a smoker at the time and flipped a cigarette butt into the same area. It too was quickly taken by the trout. I draw no conclusion from that experience other than, cigarettes can catch trout too!
IMHO - the use of uv materials helps if you have faith in the fly. If you think the uv material does squat or makes no difference, your results will probably confirm your previous opinion.