The biggest market for inverter
chargers is the home alternative energy market and the instructions reflect this.
instalations require a different set of compromises.
I think the the ABYC guidelines are a sensible standard. I would suggest meeting or exceeding these minimum satandards.
Placing the Inverter/ charger
close to the batteries is desirable solution and helps reduce wire size, but within 5 feet is not common. My own inverter
( and charger) is about 3m (9 feet). The round trip from the house batteries is double this. This sort of distance is typical.
The batteries are placed as low down as possible in a boat and this is not generally a suitable place for electronics
If you can place your 3kv inverter /charger within less than 5feet of the house batteries and are happy to use no conduit when passing through bulkheads the battery box
etc you just meeting the minimum standards with 4/0 wire.
For most installations I would insist on something larger.