What brand of system do you have on your J? I am thinking that your genoa/jib may be about equal in size to my Jeanneau Arcadia. 220# for my 100%, 155 is 345#. I would assume a 4-1 to pull forward?
This is more of a "what do you have?" different question than original to see if an equal will work for me.
She drives me boat,
I drives me dinghy!