Auto body repair & detailing: Saturn rear lip spoiler, factory spoiler, cobalt ss

Question
I have acquired a spoiler off of a 2007 Cobalt SS and I want to put it on my 2002 Saturn SC-1 but the way they designed the trunk I have to keep the flat lip on the trunk or do a bunch of custom work that I am not willing to do. I have discovered that I can cut the hollow factory spoiler and reshape it to suit my SS wing. The question I have is what should I use to mold and seal off the top of the factory spoiler to the bottom? 1 person says metal mesh and bondo, and another person says fibreglass. Keep in mind that the spoiler is hollow in the middle made of polymer, not ABS. Your help would be greatly appreciated.

Answer
There are structural adhesives that will do the job for you. If I understand you....you are trying to reshape a spoiler to fit and need to know how to attach it to the trunk lid ?.

You could use your friends suggestions but both will fail over time due to the stress.

2 part epoxy glues are used as well.