I catch and release more smallmouth on yellow body/white hackle woolie-bugger (size #8) than any other fly.
The smallies at Beaver Creek State Park in South-East Ohio just slam that fly...
I caught a few 18+ inch smallmouth there, but mostly in the 12-16 inch range.
I like to fish then just before the dam, right where the water bulges at the rock shelf, it's a smallmouth bananza... :hehe:
I also had limited luck using a purple rabbit strip zonker type fly, these seem to do well during heavy overcast days and just at sunrise and sunsets.