"Jackstay"?? To what are you refering, that term doesn't seem to apply to any part of the O'DAY 19 rigging.
The 19 has a forestay, backstay, and upper and lower shrouds. Am I to assume that the chainplate on the portside pulled out of the deck? I see that the chainplates on a 19 are really just padeyes bolted through the deck. The fix will involve repairing hte deck and I would add backing plates under those padeye locations. If you need technical answers, give Rudy Nickerson at D&R Marine a call (508) 644-3001
www.drmarine.com Rudy has e-mail, but a phone call will get near instant answers, an e-mail may get lost in the shuffle.
PS: I found a pic from another 19 owner showing how he fixed the deck core in hte area of the chainplates.