I fail to see how it's at all like composite building - it's a moulded product. Also note: frozen and freeze dried for two days. So if you want to make boats out of the stuff, you have to amortize in the cost of two days (per unit) usage of a thermally-regulated vacuum chamber large enough to put a boat in, which is a pretty expensive piece of kit.
Also, how long is the sonication process?
Making boats or surfboards out of the stuff sounds kind of pointless. As you already clearly know, the ideal boat hull is a twinwall composite, where you have composite layers of high tensile fabric bonded to either side of a lightweight foam or honeycomb core - the latter existing primarily to space the former out. If you replace the inner layer with aerogel, you're only cutting out the weight of the foam or honeycomb - and foams and honeycombs are already quite light. I mean, you'd save some weight... but enough to justify the cost and difficulty?
I guess if you're going really upmarket... after all, some people buy Monster cables ;)