I just did it on my 139FK, I used DICOR self leveling sealant. I just ran the wiring on the outside, dangling down from the roof. Since all I'm doing is recharging the battery, I kept everything outside.
The name's Jeff
2005 Fun Finder T139FK
2008 Jeep Wrangler JKU
I just installed one on my 189FBS. Installed it next to the air conditioner and behind the refrigerator. I ran the wires up behind the refrigerator and out the vent and connected to the solar panel. I also used the Dicor self-leveling. Nice stuff.