That's probably a good point about flexibility and spider cracking. I had a Magic in Kevlight layup and it had quite a few spider cracks. As I recall all of them were in the chines/sides where there was no foam core. I don't recall any spider cracks on the bottom of the hull and it went over plenty of rocks and gravel bars. I remember watching one happen when I pulled up to a dock and a wave gently pushed the canoe into a small bracket/bump on the dock. It was a very mild impact but that minimal force was concentrated in a very small area on the side of the canoe. It flexed inward and immediately spider cracked. I was shocked as I wouldn't have even expected a scratch due to that contact.
Alan
