All of these threads about powermeter accuracy have gotten me curious. I zero my Powertap regularly but haven't compared it against anything else, and I sold my second PT hub a while back so I don't have anything to compare.
I've seen mention of a "stomp test", but don't really know what that means.
My thought is just to level the crank arms, hang some weights from the cranks, set the PT on torque mode and calculate the torque I should be seeing. Do this with a few different weights, plot the line.
Any better methods?