Running a risk of beating a dead horse to death, the rear tire of my TE has now been lined with the inch wide treaded base of an old kevlar tire. Base enclosed in an inner tube just as was the flashing. I think the inner tube will help keep the liner in place and protect the air tube from its edges.

Might not totally stop sharpies, but will be double trouble for them. I expect this arrangement to be trouble free for thousands of miles and many tires. There is a 'green' element what with the old tire being recycled as a liner.