On Wednesday, March 10, 2021 at 4:41:53 PM UTC-5, Bob Kuykendall wrote:
On Wednesday, March 10, 2021 at 12:08:24 PM UTC-8, Roy B. wrote:

1) Are you saying you actually sand the Mylar taped surface itself to improve adhesion?
Yes, I sand the underside of the mylar where the tape goes. It seems to have no ill effect on looks or functionality, and it definitely improves adhesion. As JJ has noted in other posts, you really only have to sand the portion where the adhesive tape goes, but it does not hurt if you sand more area than that.
2) I have something called a "wallpaper seam roller" ( a 1" wide hard roller on a handle) that seems it will do the job of you 2 ball bearings. Does that make sense?
That tool will probably work just fine. However, given how much pressure it takes to do right, and the sheer length of the mylar seal, you might wear the tool out before you're done.

--Bob K.
The wallpaper seam roller works fine; I use the same proceedure described above for aligning
the mylar.
The section behind the dive brakes never stay on for a season; as a test i tried Shoogoo as adhesive
it makes a better bond but is more trouble to apply. It needs 24 hrs and 20C to cure as the
solvent has to evaporate from the seam.

JMF