I had some time this week because of the rain so I made a call to Life Line. My assumptions turned out to be correct. The reps suggestion providing I had the space was to use the 16 size 6 volt. This set up would yield 53 hours and would provide the owner with 100 extra cycles.
Bottom line, weight, size and cost should be your criteria. Assuming you will only use 50% of the capacity two 12 volt 30Ht’s will weigh around 200lbs and will set you back nearly 1000 dollars. 18 to 19 hours at a 8amp draw will be your capacity. Two 6CT’s will weigh 180 and will give you 18 hours. There cost would be around 860. Two 16T’s will tip the scale at 238lbs and cost nearly 1400 dollars. Subjecting them to an 8 amp draw and using only 50% of there capacity would give you around 25-26 hours. Don’t forget I was told this battery will provide increased cycles.