yep, I've got 40A of solar on a 30A controller now and its still hard as hell to max it out because in the real world conditions are not ideal, and if they do its for very fleeting moments.. that top 25% is very hard to tap into, you need like a sun tracking setup and to minimize all other potential losses (heat/wiring/latitudes/etc) to get >75% rated output consistently and for long parts of the day.. then how long will your bank take over 15A in bulk? A really long time is spent in absorb and if your panel is getting full power its all going to waste when the battery is only interested in a fraction of that unless you just start turning on loads because you can basically run em entirely off solar, like fans and stuff.
Mobile Solar rigs are difficult with camping, constantly changing locations, geography, weather, forest density, etc throw so many variables at you that you have to design a system that works in the worst-case scenarios if its something you need to always perform, which is many times bigger than most people have the capacity of carrying or willing to spend..