So, I came across this, and since there's a lot of complaints about Jag headliners separating: https://www.jagheadlinings.com/produ...adlining-board

They ship to US. Prices look reasonable. Flexible product will fit through doorway and unroll into place on many models.

I have not tried it; and the flexible headliner may not have the material "inertia" to deaden sound, since it appears to be a thin flexible plastic. Not clear whether this replaces the existing headliner board, or presses into place over it after cloth is removed.

But, if it works, it could be a very good solution for loose headliners.