Partial Sagging Ceiling Solution
Here is what i did to help the front headliner stay up.
As you can see from the picture I wired in matching ceiling light in the front section, not only does it help hold up the liner but the extra light is a bonus.
Also for some strange reason I discovered another AC vent ( over the passenger side ) that was covered by the liner. It just blew cold air under the liner when the AC was on. I ordered two new vents to match and installed them to parallel the others on the ceiling. Driver side vent was not functional.
Once complete the liner stayed up perfectly except on the far right passenger side.
I removed all and reglued the liner then reinstalled all the fixtures. Hopefully the glue will hold on that far right side in the summer heat, if not i may put another faux fixture up there to resolve the issue.
It's next to impossible to remove the old glue to get the best results so this idea seemed to be the next best thing.