Speed,

Almost everyone I know uses two batteries. Before you install those retracts, read all the RCU treads. There are wing and retract fixes to keep those tracts from twisting. AND they will twist and bend the jack screw mechanism.

I don't have time right now to full explain the fixes, but if you install a second set of housing blocks in the back of each retract, you will keep the mechanism from twisting. This fix is detailed in the treads.