I'd be verifying the chrono results themselves........I get almost those identical numbers out of my Allegiance at 30".......and 60#[:-]
My 410gr A/C/C 3-60'swere shooting278fps with a fully loaded string (loop, 2 tied in nock sets, leeches and Tru-Peep) That's 70ft lbs of KE at 1" less draw length and 10# less draw weight.
(Granted the Allegiance is a faster bow but consider the specs I'm shooting)

Even with smooth mods at 31" you should ge getting high 70's to darn close to 80ft lbs on average.

Something is screwy with the calculations or chrono.

What was the BC number that it shot that came with that bow?
Even the slowest shipping SMOOTH mod on 30"/70# bows will shoot 70ft lbs of KE.......the speed mods at the low end for a 30" bow will do 74-75ft lbs.
With an extra inch of powerstroke the numbers you are getting don't make any sense