When you say regular fellas, what weights were they? Also, did you have fuel for 2.5hrs and 5gal in reserve? That would equate to about 25 gallons wouldn't it? Now it's a long time since i flew a 22 but did you do a weight and balance and mtow calc?
say 150lb for fuel, weights of guys at 180lb each? 510lb + a/c = puts it very close to the mtow. If the guys are heavier than that, then you'd prob be over. Not much surprise performance was down a bit!