https://picasaweb.google.com/m/viewe...75016574624786
Pics of the 40'ers sprit the day we bolted it on. That's not the finished bobstay, just some line to hold it firmly in place. I think if you scroll through the pics you can see how it was made. They successfully raced the boat to Hawaii that summer, so it's gone that far at least.
Here's the drawing:
http://4.bp.blogspot.com/_5HeG270aMb...00/40Sprit.JPG
Note I'm not a pro, this was done for some friends I race with. I crunched numbers to the best of my ability, and had access to another NA-drawn plan to refer to and validate my figures. I present it just for your information, not to solicit work, nor would I guarantee this design would work for you.
Your fg covering will add abrasion resistance for sure, probably something more important for a cruising boat that deals with anchor chain regularly. If you could cast the metal part into the sprit, maybe you could get 100% contact. The problem as I see it is the steel will still be assymmetrically loaded, with the bobstay trying hard to pull the bottom aft. Since carbon doesn't give much before failure, the sprit doesn't dent and distribute the point load away from the point of contact. Maybe the glass will address this, I don't know. I do know soft attachments are easier to keep from slicing the carbon though.