Interesting info on the Mako! Drilling a 1/2" hole through the glass of the keel stringer would weaken it considerably and possibly create enough of a local stress concentration around the hole to cause cracks or delamination around it and down the sides of the stringer. However, that doesn't mean that's how they pulled the SeaCraft hulls from the mold, although maybe it might apply to the Tracker models. I believe Strick and others have found evidence of a loop built into the laminate up in the bow area of the 20' hull that was used to attach lines/cables for pulling the boats out of the mold. There appears to be some tumblehome built into the transom of the 20, so it makes sense that to pull that hull from the mold, you would have to pull it up and forward at the bow; probably could not remove it by lifting straight up at the transom.
Can't disagree with the advice to rip out and redo the keel stringer if you want to do extra work, but I question the need to rebuild it heavier than the original. Moesly used spruce stringers in the 21 before he started using hollow fiberglass stringers, and I remember Skip telling me that Carl said it really didn't matter if the wood rotted out because it was the glass wrapped over the stringers that provided the strength. That's a fact that's pretty easy to prove by comparing the bending stress calculations for a solid vs. hollow beam.
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