Couldn't find my Jann's Netcraft catalog, but I checked my Barlow's Tackle catalog and this item is an exact match for the Bass Spider Fly. Called Umbrella Ripple Skirts with Trailer. http://www.barlowstackle.com/Umbrella-Ripple-Trailer-Skirts-P2853C115.aspx
Looks like 041 would work if you wanted to tie the same color that in Eastern Fly Fishing.
The nice thing about the pre-made skirts is you can build up a thread base on the shank coat with your adhesive of choice and slide them on, just leave enough space to finish the head of the fly.
As far as the body goes. It reminds me a bit of the Calcasieu Pig Boat. What I do when I'm tie the larger ones where I use spinner bait skirts is tie in a hackle in by the tip on each side of the shank and then one piece of medium chenille on each side of the shank. I twist the hackles and chenille together tightly and when wrapped it creates a nice tapered body.