if you want to rake your mast further aft, and it is already as far aft as the forestay chainplate allows, then you are in exactly the same situation as the hobie 16 guys about 10 years ago

in their case rather than lengthen the forestay most just added a 2nd chainplate. now that hobie has realised that the hobie 16 goes better with more rake they have lengthened the forestay itself so owners don't have to add the extra chainplate/adjuster

ie i suggest you add a 2nd chainplate to your forestay bridal before buying a longer forestay

edit. rereading your last post it sounds as if you have NO forestay chainplate/adjuster, if that is so, get yea down to your local chandlers and get one

this is what you should be looking like

http://picasaweb.google.com/lh/photo/6kfFxrtYvhb5YCVHBPxSRw