Greg,
As Max said, you will need double lifelines all the way to your bow pulpit. The link in the SSS Standing Sailing Instructions to the ISAF is broken. You can find the regs at:
http://www.sailing.org/tools/documen...5B11794%5D.pdf
Section 3.14.5 makes it clear that you do need the double lines. However, nothing in there says you can't use high modulus rope tied to the stanchions for the intermediates. If your boat was built before 1993 the ISAF regs state that no vertical opening can exceed 22 inches. So, get out your tape measure and see if you also need to run the line around the pulpits or just up to the pulpits.