Joined: Aug 2010
Posts: 12,727
Likes: 2,105
From: Madison, WI
Bikes: 1961 Ideor, 1966 Perfekt 3 Speed AB Hub, 1994 Bridgestone MB-6, 2006 Airnimal Joey, 2009 Thorn Sherpa, 2013 Thorn Nomad MkII, 2015 VO Pass Hunter, 2017 Lynskey Backroad, 2017 Raleigh Gran Prix, 1980s Bianchi Mixte on a trainer. Others are now gone.
Skip the backpack, get panniers or a trailer. I am a pannier user, some however prefer trailers. I suspect that if you had tried to mount a 4,500 in^3 backpack on top of your rack with a load, that you would not be asking if that will work.
As a backpacker, you have almost all the camping gear and the fitness level you need. But, you need a good bike and a way to haul your gear. Also need some bike tools and spares and the knowledge on how to use them.