Did we recommend pushing 55 amps 30' through #6 to charge 4x GC2? :(
#4 direct is an obvious help. If pulling wire consider pulling 120vac to mount the converter close to the battery. NEC is not very big on parallel conductors so you need to replace the #6 or move the converter.
Possibly a second converter to clamp on the battery when fast charge is wanted. Although it may actually work good enough as is so maybe give it a go. The hydrometer should rise within a week and with some exercise this summer I am thinking the charge time will improve.