So here is an approach I think might work.
I obtained a fine screen from a tea fliter and cut it out.
Cut a piece for the hole.
So the next challenge is how to hold it in place inside the tube.
1. Use a string like floss attached to the center and pull up while applying the steel impregnated JB Weld. Challenge is to keep the right amount of tension for a period and then cut the string.
2. Insert a balloon into the TT through the hole in the seat tube and head tube. Blow it up just enough to hold the screen in place. Challenge is getting the balloon in and it not rupturing.
Thoughts?
I am working on determining the approach for touch up paint.