I've known some panels to be called "self regulating" that were actually designed to put out less voltage then "regular" 12 v panels. Somewhere around 14 Vmp. This seems like a really bad approach as it simply wouldn't charge very well.
I have to disagree than 50 watts isn't enough solar. It all depends on how you camp. On my first 24' TT I had a 75 watt panel. I used an inverter to power my toaster, microwave, and TV. I had plenty of power.
On my current TC I've used a 55 watt some and now a 30 watt panel. When dry camping I have plenty of power for an extended weekend of lights, pump, ref., vent fan, etc.