Striker, i haven't used one personally, but i know someone who has run 4 cell with reciever pack with a zero extreme. You will need to remove the red wire from the reciever plug of the speedo, and then switch both the pack and speedo.

Not sure about caps, don't think you need them but i have never tried one personally, although i have run one with every other speedo. Assuming you are refering to "Power" caps!