I think you'll spend more time farting around on load lifter risers than you would finding an old kelty or camp trails frame to assign to canoe use! I don't think you'll get enough lift or separation from your back using typical internal load lifter risers. I wouldn't bother attempting this on my Kifaru, when I have a Dana external to use.
With my method, you need to leave the portage bar installed, and that leaves lots of headroom in the void fore or aft of the bar.
With my method, you need to leave the portage bar installed, and that leaves lots of headroom in the void fore or aft of the bar.