I used red fox tail for the belly and the back of the one on the left, calf tail (yellow belly, brown/yellow back) for the one on the right. Most of the bulky look comes from tied in pectoral fins and dorsal clumps of rabbit fur.
I highly recommend Clouser's book if you like his patterns. He's a great teacher (I learned how to tie from him in PA) and his book is extremely well written and photographed. The patterns above don't follow the recipe precisely.
Hook Mustad 3366 or similar
Tail: rabbit fur strip pierced by the hook and tied in just behind the eyes
Pectoral fins: just behind eyes on each side, rabbit fur
Belly: (top of hook) calf tail
Additional belly clumps of rabbit fur, one tied just behind the eyes, one just in front of them
Finished by final back of calf tail
Flashabou as desired (placed beneath the final back of calf tail...I didn't use it)