The last waterproof USB power supply I installed on my 2011 RTS kept getting wet, and finally shorted out. Had it mounted under the dash but still managed to get soaked during some of our torrential downpours.
This time I decided to try something a little different on my 2015 RTS. This one is facing down, so hopefully that may help the water from collecting inside the USB ports.
I install this one in a mount on the speaker with a waterproof switch under the dash. That way I can turn it off if it does get to raining too hard. If it doesn't work, all I'm out is a speaker cover.
I was surprised how mush water gets to the dash when it is really pouring. I replaced the gauges with power plugs but they have a rubber cover, so they didn't get water in them, as I pulled what I had plugged into them and closed the covers. That solved that problem and the GPS, radar det. and dash cam weren't really needed at that point. It was really pouring. Normally, I wouldn't ride in the rain but 900 miles from the barn and few options. The way the whole area was running with rain, I don't know if your option is better, but obviously, it can't be any worse.
One of the hardest decisions you'll ever face in life is choosing whether to walk away or try harder.