Very good question!
Actually, I was able to tiller this bow to a 16" draw without the cable and with grain violations on the back. Then I added the cable and wrapped the non-bending portion of the handle and tips only. I then glued the cable to the back so it wouldn't move. The cable did come loose in some spots but I just wrapped those areas with a little bit of thread that could be removed quickly if needed.
The hardest part was making sure the cable was riding exactly on the crest of the rounded back. I think if I carved a channel down the back, for the cable, it would help even more. I think a carved channel was used on some authentic bows as well.
After final tillering, I added more wraps.