I am not an EE myself, but have access to some of the best on the planet- these are the guys that developed spray on solar panels, PV tent/sail material, and even PV boat carpet (expect to see it as an option on Tritons in a few years). To a man, they all tell me that it is not possible to recharge a deep cycle battery using solar. At best, you can get a trickle (maintenance) charge. They have their usual technical gobblydegook explanation, but the bottom line is it ain't happenin'. I tried small wind turbines to get a charge, my property in the UP doesn't have the best topography for it- high steep shoreline, lots of tall pines- even resorted to placing the turbine posts inside my dock posts, and the best I could do was 5 days of charge in 20 days of fishing. I ended up taking the turbines to an outpost lake in Ontario and installed them for the outfitter, he has the perfect property for them and says they work great to recharge his batts.
I have used solar in Iraq and AFG to charge small stuff, optics, radios, phones, lights, even ran my computer off of solar for a few days- the best panels I found were by Brunton, they make a nice roll-up panel that is very robust and hard to break.
To solve my batt charging issue up at the cabin, I ended up buying a small Yamaha e1000 generator- about as quiet as an idling car, sips gas, and has a bunch of other applications as well. The small 1000 size goes for about 700$, but to try and get enough solar + converter + regulator to do a half-baked charge on your deep cycle batts will set you back well over 1000$ and still won't give you a good charge. I know it isn't what you wanted to hear, but I have the same issue as yourself and this was the best solution I could come up with for me.