Your bow is probably doing about 270fps

Your bow is rated at 30"/70# 350gr arrow with a bare string and that rating is probably high end so these are approximates:

-3" draw = 30fps
16grs over 350gr = 5-6fps
string load= 8-10fps

Whisker biquit?.....might equal another 2-3fps
That's a subtraction of about 45-50fps from the rated speed.

I'm not too wild about Spitfires for light arrow mid speed type combos.....sure they'll be OK with perfect broadside shots and probably work most of the time but I think there are better choices for you.
The NAP Scorpion or the new 3 blade Rocky Mt. Snyper would be a better head for your set-up. More modest cutting diameter and open faster upon impact and require less energy to keep em' moving all the way through.