Have either of you checked your wheel run out? It *shouldn't* be an issue given that your shakes are speed relative, but run out can cause some strange problems. Those of us with locking ring style wheels have them mounted to the hub using little locking wedges with large nuts holding them on. The problem is that there is nothing to center the rim and keep it concentric around the bearings. This must manually be set. Jack the front up and spin the wheels with a reference mark on the ground. Watch to make sure that as you spin it it isn't getting closer-farther-closer-farther-closer-farther as you spin it. If it is I would suggest that you back the nuts off (but do not remove them...you just want them loose as a starting point). Then, spin it over with your reference mark. When you have a part that is getting farther away from the mark tighten the closest nut a little. This will force the tire out at that point. Work your way around slowly torquing them all down. Eventually you should be able to tighten all the nuts to spec without it moving and with it trued up.
Also, do you have radial or bias ply tires? Bias ply tires will get flat spots from sitting that can take miles to smooth out. You oughta see what my super swampers look like when sitting. I have actually witnessed a set of swampers that sat at 5 psi overnight cause a PCM to flag a multiple cylinder misfire because the flat spots were so large that they actually caused the crankshaft to speed up and slow down enough to trigger the code. It's not often that a P0300 can be solved with an air chuck.