Please share your method for re-installing the drain plugs for the sunroof drain. The driver's side wasn't that hard, the passenger side is eating my breakfast, lunch and dinner. Thank you

 

I'm not sure who you're asking, but as a four-times veteran of the process, here's my take:

You can get access to the back area by removing the apron molding that goes under the windshield wipers (The two center fasteners are 90 deg turn catches, different than any other Volvo fastener)

The Elbows lead down through the firewall and project through a slightly larger access hole into the space below the hood hinges. In its final position, the tip of the elbow can be felt in that larger access hole.

I used, at various times, a wire leader inserted into the hole first and a 1/2" copper pipe "tool" to snap the elbow into the hole. The dash molding also can flex slightly to give a little more room.

My last resort would be threading a longer piece of tubing through both holes and joining it to the down pipe with some sort of coupler.