HELP! Stilly bug nerd needed - what's this mayfly hatch?

fishwater

Human Being...a work in progress
#1
Emerging mid-morning to noonish on lower North Fork Stilly in head of pool below long, shallow glide. A fair-size mayfly, not BWO-size by a long stretch. Duns with a green/yellow cast to their dramatically segmented abdomens. Look to me to be an Ephemerellid, as they are kinda chunky. Approx 1/2 inch long, excluding tails. The cutts are loving them!