I'm not argueing the fact that your Spitfire's took more energy......but you also need to think about there is a cutting diameter difference and overall cutting surface difference!!

I have blown through many whitetails with Spitfires with plenty of room to spare ........but I have had several 70+ lbs KE set ups !!

The Tekan looks nice !! If the Steelforce fly good for you why not use them ?

I guess the big question is what result are you hoping to get ? Maxium penetration......biggest entry hole........biggest exit.....best bloodtrail........easiest to tune......etc. ???