I used 3M Super 77 adhesive for my MetroAmp 100 watt panels.
I would say that I would only put the glue on the chassis. I put the adhesive on the chassis and the back of the panels and there are a few places where you can kind of see adhesive build up showing through. So, I wouldn't put any adhesive on the back of the panels...
I usa Super 77 too. The new silk screened panels don't have the issues with the glue that the old ones had. You can even use superglue.
But contact cement is better.