Seems to me the main problem is that everyone wants yadda yadda designed to fit their specific gun with such and such forearm and such and such barrel etc. It doesn't take a lot of brains to know that the ATI shields are designed to "BE FITTED" to as many diff guns as possible. That tends to imply that some minor fitting might be necessary on your, the user's, part. That back clamp thingy....if it's too snug on your barrel, open it. If it's too big, close it. If the forearm rubs, fix it. If you don't like the metal on metal contact, use a strip of thin rubber as was suggested. I mean, come on. Did anyone not know that??? Here's a tip; if you buy such and such a part, there's a pretty good chance that it might not perfectly fit the other half a dozen parts you've assembled. If it doesn't, that in no way makes it a bad part. Use your brain. Fit it or trade it.
And I have a couple of the Mossberg shields on my guns....and guess what? There's forearms that that shield won't fit.