I’ve finally cracked my first boat. More tragic, it’s a Jackson crosslink so welding is not an option. The crack is about 6” long just right of the pillar and not spread out by lots of oil-canning. My plan is to drill the ends and cover the inside and outside with hippo patches (super sticky like creosote / roofing tape, but with a solid backing that I’ve heard holds up much better).

As a newbie to this, my question is: how big should I drill the holes??? Basic physics would suggest that the larger the hole, the larger the area that the stress of the crack will be spread over, so more stable… but the bigger I make the hole, the more room the crack will have to move causing spreading, oil-canning and subsequent failure… or maybe I’m overanalyzing this and it doesn’t really matter as long as the ends of the crack aren’t sharp...

Anybody have some sage advice on what's worked in the past?

I fixed a crack and its still holding today by doing this: Drill both ends like u were thinking. Then clean the surface inside the boat with a little acetone on a rag. Then I spray a coat of 3m adhesive around the area. Next I take some mesh drywall tape and put a layer over the crack. Next I use WEDI and spread a layer about 1/8" to -1/4" thick with a taping knife. (WEDI is a sealant used for waterproof tile shower systems)The key to this is lets say you have a crack 3" long, you would need to make your patch with the mesh and WEDI at least 4" x 6" so it has enough surface area to stick and flex with the boat. Pretty sure u could glue your a##hole shut with this stuff.I patched a friends boat as well with this system and they actually cracked the boat again in a different spot but the original crack/patch held up.