We too are believers in solar for use with the trailer.
We have gone many days with no power and have always had our two batteries up to 100% by 10 AM. And, in the summer, the further north you are all the more reason for solar (longer days = more sunlight). But, having said that, we find that full sun or cloudy days make no difference to the charging.
We have a good friend with a 5th wheel. We tried to get him to have some solar panels installed; he opted to buy a generator to recharge his batteries when boon docking; says he really doesn't need the 110V stuff.
Unless you absolutely have to have 110V for something there is absolutely no reason to be using a generator to charge batteries when off the grid. This is one of the absolutely best things we have on our 30' Classic.
Given that so many things will operate from 12V
(Computers, stereo equipment, lights, fans, etc., etc. there really isn't much need for a generator.
OK, my weakness is my compressor and I am too cheap to purchase one that runs off the PTO on the truck so I haul a small compress with us and use the generator for that to get the trailer tires up to pressure prior to moving out in the morning. And, it is nice to blow off all the dust when we return to camp after riding in the dirt on our enduro sidecar. :-) But, this is something nice to have, not a necessity.