OK, I LOVE this profile! I never had problems in the past using it, and the rattle never bothered me. At the shop I work at now that moulding is not carried on the sample wall. Recently I had an order that it would have been perfect for, so I pulled out my specifier and sold it. When I got to the shop and asked the person who fit the job what they thought of the frame I was met with violent complaints about the rattling. So what? You didn't have to mess with building shadow box strips, right? Another person mentioned that they used to use it at a different shop and they would always have to replace the glass on jobs with this frame because it always broke. I never had that problem, but maybe it was an isolated incident and they were exaggerating but still... It seems very probable that the glass would be at risk of breaking if it was rattling around in a metal frame.
My suggestion was to use acrylic. No rattle, no break, no problem.
So that's my 2 cents on this frame and I am still going to suggest to my higher uppers that we carry it for its design benefits and minimal labor, rattle or no. Some people just like to find stuff to complain about, anyway.