Medusa 36-80 or 36-70

Alright, I can make a harness and run my 3S in series to get 6S but that would only give me 5000mah, basically cut my runtime in half. Now say I do this what kv would be good for running 4S and 6S??? the 2000kv or lower than that and change gearing to make up for the change in batteries???

I like the long runtimes that I am getting now, that is why I was looking at running only 3-4S with the 36-70-2300.