your hurting my brain...
if clamp dia and bar dia match then you don't need a shim pick a stem you like or bar you like and match em up it's really that simple
27.2 is your seattube dia, I am certain and the pic of the other kids masi with the EA70C post vilifies my hunch because it's the smallest diameter Easton makes in the model.
WHY DONT YOU DO THE FIT?! ... figure out what stem length is recommended for YOU.
what you are asking is sorta like asking a shoe salesmen to tell you what size shoe you wear and refusing to let him measure your foot.