Posted this a while back but i thought id repost it here, A solution to repair correctly but doesnt address the fact that futures and FCS need to address the issue with a bigger footprint to take the forces associated with large area fins;
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Ive had three futures boxes go on my dhd twinny. contemplated selling it and lucked into talking to a mate that shapes quite a few boards for our local crew, majority been twins. He said he has had the same issue when he started shaping so shifted to doing glass ons only. He did come up with a cool hack to stop the issue through years of R&D. So far 4 months later, surfing solid waves and big fins, not a single blow out or hair line fracture around them. His method is to create a slightly larger well for the box, drill two holes through the rail, and pour resin then feed through wooden dowels all the way to the outside of the box. the leverage of the fin is then offset by the surface area gained by the dowel. works a charm.