I dealt with the USB power outlet issue when I started using the Stratux ADS-B receiver transmitting to a Nexux 7 tablet. I purchased a neat looking dual USB outlet from eBay and eagerly installed it in the RV-6. The thing caused so much static in the KX125 nav/com that it was unusable. I next tried a couple of USB cigar lighter adapters purchased at auto parts stores and they created the same problem. One day I stuck an el cheapo USB adapter from Walmart in the power outlet and it worked perfectly and I still use it today. Just lucky I guess......
I've since taken the unusable dual USB outlet, stripped out the electronics, and wired it to one of these:
https://www.amazon.com/HOBBYMATE-Swi...&keywords=ubec
This device is quiet and works very nicely.