Yeah!, the flouro v-posts with glass beads are my play on the Avalon Crab. They give plenty of rattle...cause the fly to sink upright and stand on bottom in the "defensive crab posture". When dragged along the bottom, the fly nods and walks like crazy. They also tend to act as a weed guard aswell because the fly straddles the grass instead of sinking down into it.
Good observation about the furry foam. It's a very easy pattern to tie. Once the legs are tied in "merkin style"...the furry foam cut-out (I made my own cutters)is glued on top of the fly , poked over the hook eye, then doubled back along the bottom of the fly which is exactly how a real crabs shell is..."not just on top" (note: the eyes are burnt mono stems crazy glued to the underside of the furry foam vs. tied-in on the hook shank...too easy!)
I call the fly a "Castanet Crab" and I also tie Merkins the same way...the "Moracca Merkin". I also have a shrimp pattern done the same way aswell called the "Castanet Camerone"