Hi Paul,
I would not mylar the backglass. Once this is done, you cannot do any touchups to the glass with mylar in place. Some of the other forums suggest that over time the mylar may actually pull more paint away. I think the triple thick would be the way to go.
I concur.
Mylar also can further damage the backglass as the heat from the globes "warms" the adhesive properties of the mylar. In addition. Mylar shrinks over time and it would end up damaging the glass. I think Gavin might have some ideas here - but I've successfully sealed backglasses using the Marvin's guide and I would recommend that you go down this path VERY SOON. I would not be handing that backglass too much as it looks like the bottom might flake off at any moment.
