I just used the solar proof on two Copper Spur UL's before our Sierra trek this year, mostly to protect the $$ flys from sun. It went on thin and I was able to fully cover and coat a UL2 and a UL4 with one spray bottle (dead empty at conclusion). I thought that the "extra" effect with surface beading would be great, too.
In 14 hours of rain, both flys wetted through by morning, and the UL2 wetted through in a 7 hour stretch the next day (dry start) but neither spontaneously combusted from UV rays. Ho ho. My conclusion is...inconclusive.
I will be talking with the BA folks about what I can do to harden the flys for that kind of rain, however.