9/32" is rated at 9400 lbs and weighs 17 lbs per 100 foot.
3/8" is rated at 16000 lbs and weighs 30 lbs per 100 foot.
Weight aloft is not good.
What needs to be determined is what the breaking strength of the chainplate is and the associated bolts, clevis pins, tangs etc. Also the force on the sail can be calculated to get a realistic idea of how much force there really is on the shrouds.
I went through this a while back and came to the conclusion that upgrading only part of the system (ie just the wire) was not going to do me any good, and upgrading everything seemed unrealistic.
Bud Taplin might be a good source on this issue.
Also, some have gone to the next size up on the headstay, backstay and boomkin shrouds. This seems like a good compromise...the boomkin shrouds in particular are more loaded because of the angle they are mounted at.