Steel; Set your cams so that they would be even and at full rest. Tape them secure to the limbs. Take a string, any long enough string, tie a loop on one end. Do the draw string first. Make the necessary wraps and add the other loop. Now do the same for the take up or power cable. Once you have a slight even tension on both your strings, I would subtract 1" and build them.Looks like you have a beautiful job on the cams and limbs. This , is like most things of this nature, trial and ERROR. You might hit it right on ,maybe not. Also don't forget, you can help your self a lot by twisting the strings . When you make them , I would allow about 1/2" longer when you set up, then twist the string to get your measurement. On both strings.You can use dacron, you can also use some of the newer super materials.If you've never done a string before , google , make bow string. There are several good vids on this. If I've left you in a dither just come back , I'll try to help you. Good luck, Oh, take your time, don't rush. Rome wasn't build in a day, coarse, I wasn't running that job.I'm sorry , I forgot to tell you how many strands. I would try 24 strands. Now don't forget, that will be 12 complete loops. That would be using B50 dacron.