in the xmods mods and projects section in this forum there are i think two different 6 cell upgrades for the evo cars and trucks.

this is how mine was done.

1. on the car there are two wires coming from the battery compartment, 1 red , 1 black.

2. cut the red wire apart.

3.then take your new 6 cell battery holder and connect the black wire to the red wire on your car that comes up from the battery compartment.

4. then connect the red wire on the 6 cell to the other red wire on the top off the pcb.

5. plug in your batterys and test to see if it works.

6. solder these joints together or use deans plugs if you want to be able to switch from 4cells to 6cells.