Your bank size is definitely smaller than desired when under way. Even going to 8 golf cart batteries you will need to run a generator
If you get the solar charging
squared away six golf cart batteries should be sufficient for at anchor
in the tropics and sub tropics.
It should be noted that the batteries don't need to power the boat for the whole 24 hour period. The solar
cells should be carrying the load while they are charging the batteries. I would guess that with a good solar set up the batteries would be under discharge around 14-16 hours a day. Hopefully maybe even less than 14. An additional thought is that though running a genset or main engine
to charge the top 15% of the battery
capicity is seldom done because of the batteries slow acceptance, if enough solar is available the battery bank may be completely topped off every sunny day. Input from folks using satisfactory solar would be interesting.
6 of the Duracell GC2s 645 amps X 30% = 190.5 amps ( as I figure it)
645 amps X 35% = 222.25 amps (as Charlie and many others figure it.)
Assume solar can handle the load 8 hours a day: 16 hours = 2/3 240 x .66 = 158
Six of the golf cart type batteries should stay happy a long time.