Did this on a Prindle 18 years ago, and ended up going to the Harken setup which I feel was a cleaner application.

Your going to need to shorten the upper forestay along with the pigtail as well to accommodate the top roller barrel along the bridal wires. I believe we went with 2.25" on the bridals and 3.5 on the upper forestay pigtail

Give Joel @ Murrays a shout. He keeps an encyclopedia on this stuff and can hook you up with all the messurments