The Routeburn river has always looked like it fitted into the `too scary` or `too hard` box for the majority of packrafters. It does hold a grade of class 4-5 in the Graham Charles NZ Whitewater guidebook, pg 266.However while scouting this run from the Routeburn bridge down to the Lake Sylvan bridge it was noticed that from Weka Flat it was much more feasible as a classic grade 2+ run. It is short, 2-3km, but very sweet.
https://www.packraftingtrips.nz/routeburn-river-ii-weka-flat-to-sylvan-bridge/