Re: DIY Bowsprit
If you are talking about light air cruising with a modest sized chute then you don't have too much to worry about assuming your deck is structurally sound and not spongy. The Selden kits rely on a couple of bolts through the deck with a backing plate to take the whole load.
On the other hand, if you think you might be tempted to try the setup out in phrf racing with a full crew hiking on a power reach, then you might want to consider over engineering it a bit!
1979 Santana 30 Tall Rig