I couldn't see a Happs bezel (as in bezel around the monitor) on that tutorial of yours. Just some dark pieces of wood covered by plexi. And no, I'm not so "groovy" with screws through the plexi covering the monitor, but it sure is an easy way out. I guess that also explains why you didn't use multiple coats of primer (with sanding in between).
But anyway, jerschwab, the way to mount the marquee retainers has to be in that plan too. If they tell you to buy the happs stuff I would imagine they explain somewhere how to mount it. Did you read through the whole thing?