The number of fins (and the sewing required) is a little intimidating, and they all need to be placed quite precisely, so that they hold down the side "segment" flaps, as well as overlapping slightly. Fortunately this turned out not to be as time-consuming as I thought, and I'm very happy with how well this turned out.
I'm not totally convinced by the eyes -- they're knit as little hemispheres and lightly stuffed, to give them a bit of a boggle-eyed effect. I think anomalocaris's eyes were raised, possibly even extended on stalks, so this is fairly realistic, but I don't think it looks good here. Possibly the sharp contrast in colour, when the rest of the body is so uniform, is what makes this look so out of place.