Upsizing does do the trick, though if I'm tying a real skinny profile body - sorta catskill in nature, a regular sized seems to do fine...though the bulk of my mtn flies are bigger bodied and the size over hackle helps keep them stabilized.
On midges for tailwaters I stick to the same size hook/hackle - again because of the slender profile they present.
Something else to consider - do away with hackle and go "Spundun style" which uses elk or deer hair, creates a terrific wing/legs profile that is easy to see and floats like a cork andis ultimatel cheaper than any hackle...no assortment of sizes of feathers and really no parachute material to use - , just a couple shades of hide...
you can get an #18 tied with a little practice finessee , but standard fare is size #14 and up - perfect for the Smokies...and easy to tie.
May you find a rise in every puddle... - WATERBORN