I have 2 60 watt panels fixed flat mounted on the roof of the RV; they are wired through a charge controller. I also have a 100 watt panel that is mounted on the side of the RV. The 100 watt panel is removable,and I connect it directly to the battery for charging (no controller). I have a 30 foot cable made up to put the panel in the sun; I intend to make another cable 50 feet long to better place the panel in sun (I used 10-2 SJ to make the cord). If you pay attention to the battery voltage, the 100 watt panel is not going to overcharge the battery.
I found the idea for the exterior mounting in this forum.
Regards,
Doug