Under the IT rules, is it legal to remove the sunroof drip tray? This is for a 1987 VW GTI 16V. I want to be absolutely certain that I understand the allowance before removing the sunroof drip tray in it's entirety so I can securely retain the replacement panel to the roof with structural adhesive.

I don't believe this rule explicitly allows removal of the sunroof drip tray metal that is fixed to underneath the roof.
9.1.3.D.8.f.
"Manual and electric sunroofs, original or aftermarket, where
the panel is not normally removable shall be retained and run
in the closed position. Components (motors, cables, rails) may
be removed provided the panel is securely retained.... All
sunroofs may be replaced with panel or replacement skin of
the same material as the original surrounding roof material."
This may allow the removal, depending on exactly what is meant by "sun roof liner and frame."
9.1.3.D.9.f.
"Carpets, center consoles, floor mats, headliners, sun roof liner
and frame, dome lights, grab handles, and their insulating,
attaching or operating mechanisms may be removed."
But under the non-VIN rule I believe it should definitely be allowed since sunroof was optional on the 1987 GTI 16V.
Line under car classifications
"Volkswagen
Golf GTI 16V
(87-89)"
So exactly which rule would apply in this case to (hopefully) allow me to remove the sunroof drip tray in it's entirety? This would also essentially create a non-sunroof car because all the underlying structure would be completely gone, except I would bond in the replacement panel rather than replacing the entire roof skin.