C'thulhu's arms and tail have been attached to the body and the slight gaps where the pieces meet filled in with Green Stuff. I'm really pleased with how this turned out; this time around, I was smart and, true to my human heritage, used tools instead of trying to just work Green Stuff with my fingers like I did back in high school/early college. I completely forgot to take "in progress" shots again (something I hope to be better about once I reach the painting stage) but all I did was roll out a small dab of Green Stuff into a thin "sausage" and then wound that around the edge of the arms and tail where they would meet the body. Dabbed some superglue onto the pegs connecting the pieces and pressed them together, then smoothed out the Green Stuff and cleaned away the excess. Simples, as they say across the Pond.
Here are some shots; I love how dynamic the figure's pose is; he definitely feels like he's lurching forward - as Lovecraft put it, like "a mountain walked or stumbled."
The one thing I'm still iffy about is whether or not to attach the wings prior to painting; I know I want to leave the head off because of all the detail, but I feel like if I leave the wings off then I can paint the back of the figure more easily; however, test-fitting the wings to the body reveals some significant gaps. I suppose I could paint body and wings and then attach them, work a little putty in, and then carefully paint over the putty to match the body as best I can.