And a patient wife!
I'm replacing the original charger this winter.. i was reading the manual on the original unit and it would seem that they designed it to simply cook batteries for 14 hours at a high voltage.. not the best design. i had the same unit on my Catalina 30 and it cooked 2 sets of batts until i realized the issue. I like the idea of just allowing the solar to float the batts though... maybe next winter when i get the bimini redone i'll have them create a perm solution for the panels to stay full time..You could try an alternative procedure for replacing the 4D's that worked well when my 4D's failed the first time at Cape May, NJ. The dockmaster at Utches Marina had a young fellow pick up a 4D and carry it up to the shop, and bring back a new one, then did the same with the other 4D, no charge. Great service!
The flex panels are a good option. I installed one on top of my RV and it works very well. I think you will want to keep them in place, though. The controller that you will install for solar power will be a smart device, and will charge the batts through all the proper stages of charging, and maintain a proper float charge. The old charger on the boat is a dumb charger and will not do a good job of charging and maintaining the batteries. I usually leave the boat charger off when I am on shore power, and let the solar controller do it's thing.