Those are great pics of the balloons on your Elise. I just replace mine too; I think another contributing factor in the life of the tire is there is a medium compound and a medium-hard compound. I got the medium on my new rears. and I have always run 26 cold on the rear and 24 on the front with good even wear on them.
Anyone running more -camber in the rear will not experience this as the insides will wear evenly with the centers and you keep that extra outer block for when you really need it! My alignment cambers are -1.6front, -2.2rear. Fine on street great at track. Toe is my little secret
I think 29 psi is the wrong air pressure, my rear A048's always wore in the middle as well with about 2/32nd's tread left on the edges when the middle were at the wear bar. I'm not sure why the factory suggests 26/29.