Definately through the cable for me. Seems less likely to ever fail.
Try this from the RipCord website:
For serving in the rest cord.
Start by splitting the nearest cable (downward traveling cable) and sliding the rest
cord into the same position as described above. The pressure of the cable on the cord will hold it in place while
you are setting it. Draw the bow back to full draw and
let down (
do not dry fire), this will cause the cord to slide in the cable and set it into position. Lock the rest into
the up position and draw the bow to make sure the cord will disengage the rest mechanism. The cord should now
be in the proper position. Trim the end of the cord next to the cable and pull it away from the cable and melt the
end and flatten like a mushroom. Now you can serve in the top and bottom of the cable.