OK, so the first sunburst fix went "bang" as soon as I put my foot on it. Literally, the first tack of a windy race. On closer inspection it suffered from three flaws: the sides of the fix were parallel, offering at least the possibility of the two faces shearing across each other; the pad underneath wasn't fully glued on, and where the epoxy had stuck I had been a moron and attached it to a moist surface; finally the fix wasn't flush with the deck when pushed hard from underneath ... causing me to not push hard from underneath and cuase the pad to not be fully glued.

What we have here is the mark 2 fix. For a start the edges of both the deck and the patch are chamfered together. This allows for a greater area of adhesion but perhaps more to the point means that much of the shearing force is taken out. Mechanically the patch sits on top of the deck and, kinda, can't fall in ... it's also thinner and closer to being flush (but not as close as I might like). The pad underneath is (I think) not as large, but is attached to a clean sanded surface. The whole lot is attached with epoxy with a higher microfibre content than before, and more of it to boot and significant wobbling and squashing got some air bubbles out before it set.
Unlike the first fix I feel good about this one. It might not be pretty, but I
challenge you to fall to bits now. Which is good, because we have the nationals next weekend....