Whatever you do, DO NOT tie the preventer solely through the clew cringle. There is not enough strength there to prevent an accidental jibe.
I would leave the clew cringle completely out of your thinking. It's an in-mast furling main, so depending on wind conditions that clew cringle could be well forward on the boom, which would not work if you are going for an end-boom preventer led forward to the foredeck. For that arrangement, you need to have the preventer line secured at the end of the boom and led outboard of the shrouds to the foredeck.
My best suggestion is to examine the available hardware mounted at the end of the boom. There may be welded eye there through which you could securely anchor the preventer line and of course tie it around the boom too. There may be a solid point for a snatch block, etc. Or something like what SD suggested, but at the end of the boom.
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Pacific Seacraft Crealock 31 #62
NEVER CALLS CRUISINGDAD BACK....CAN"T TAKE THE ACCENT