S30 was built with Navtec rod rigging - not wire.
Here are the original design sizes:
Headstay/Backstay/Upper and Lowers #8 cold headed stem rod (min breaking strength 8,200 lbs)
Intermediate shrouds #4 cold headed stem rod (4,700 lbs)
this appears to be typical WD Schock build approach, do the engineering but then make sure "entire boat can be picked up from any one main shroud plus add in a factor of safety
from the J/30 owners site - http://j30.us/blog/?page_id=322
uppers, lowers, and forestay are "1/4" diameter which the Navtec chart has a 6mm 1x19 (with breaking strength of 6,350lbs)
backstays at 3/16" would have breaking strength in the 4,500 lb range.
Didn't realize there was such a big difference - thanks for asking (wait for the J-bots to start a flame war over this)
(at the shop on Saturday trying to complete year end inventory)