nice how-to job and pictures rm -rf! fwiw, i encounter the same problem with my Conti (4-Seasons) on my rims as well (one Mavic rim, and one Salsa rim). my procedures are identical, and i've had to field-change a couple of time with simple levers (like yours), some patience, and a little elbow grease.

as Chris_W pointed out above, i've found it's slightly easier to start opposite the valve hole, and then finish at the valve, which also makes sense on my rims since the valve hole is the point farthest from the (stiff) rim weld. even so, i've done it both ways successfully. for me, the Conti tires are worth the minor aggravation; the rubber runs fast *and* sticky, which is a mythical balance to achieve.