When all the connections are clean, the cables the right size, there should be very little trouble with the 6 volt system.
I have had as good luck with the basic battery as I have spending a ton of money on special batteries.
In fact, I have had better luck. Working in the parts store I have seen more of the spiral cell batteries come back for warranties than the regular batteries.
Maybe the six volt is different because it would have thicker cells.
