Mike
You didn't say what your "factory charging system" consists of. If you have a Perkins 55 amp alternator with an internal regulator, that is the first place a change is needed. If you have a "Constavolt" Charger, that is the second place. If either of those has been upgraded already, please say so, as that will influence any advice you get.
Third, or maybe first, what are your loads? Do you have a fridge? Of course you do. Is it a Norcold AC/DC? If so, that is the first thing that should be changed, as all by itself, it will have the greatest impact on your charging needs.
I looked at Roche Point when I was boat shopping in 1994. It was very clean, shelter kept, but I can't recall the answers to any of the questions I have posed above.
Taking your post at its worst, I will assume you have:
1 - Norcold AC/DC,
2 - 55 amp, dumb alternator,
3 - Constavolt 20 to 40 amp dumb charger.
For your start load, you need at most a single 4D.
For House, 4 golf cart batteries will not be enough unless you change out the fridge for a DC only version (see "Freddy Freezer", at North Shore Refrigeration). If you keep the power hog fridge, go to at least 6 GCs.
For alternator charging, get a high output (at least 100 amps, up to 140) alternator and Most Important, a three stage external "smart" regulator. Balmar or Ample Power have excellent choices.
For the Charge from shore power, get at least a 100 Amp "smart" charger. If you get a Xantrex 2000 watt Inverter/Charger, or equivalent, your world will change.
Last, some sort of monitor system. Again, Balmar and Ample Power are both good. This is less necessary if you have a readout from your inverter/charger, as you will get much of the required information there.