45lbs is nothing for the Trizip. I've carried mine around countless Indy 1500 gun and knife shows, Knob Creeks, and 3 Blade shows now, canoeing trips, and some hiking trips. I've had it loaded with knives, ammo, guns, pretty much everything besides water.
With very heavy loads, the pack is still comfortable, the straps don't dig in, they're very breathable, and it's an all round great pack for the most part. It's a bit small overall, but still a great pack. I'm not a huge fan of waist bands (damn lovehandles ), and it's nice that you can take it off, which mine is always off.
I've never felt/lugged around a BFM, and to be honest the only reason I have my Trizip is that I found one hell of a deal on it and couldn't pass it up, but it's turned into one of my best purchases of the past 3 years.
"Have you paid your dues, Jack? Yessir the check is in the mail" - Jack Burton, Big Trouble in Little China
"Catch me in five minutes, I'll smell like hard liquor" - Al Bundy
Inducted Blade 2010- Ham67