I don't have charts and data to support my claim, but I don't think you should let the varying AT status of the anchorage line worry you. Here's my argument: if you limit the role of fabric to covering treatment, think of the fabric as an extension of the treatment - since that is how they will function. So what's the difference between using FR701 and Anchorage?
Here's the absorption data for FR701:
FR701 is nearly perfectly AT across the range of meaningful frequencies. Yes, it will generate reflections above 1000Hz - so treble reflects some
- it's still going to transmit almost all of the energy.
Here's the absorption data for Anchorage:
Anchorage is less transparent, clearly. We see the there is a small amount of energy that will be reflected at all frequencies, but it's fairly linear across the same range of frequencies.
I'm going to launch into an argument here that appears to be supported by numbers - but I have no real idea if it's appropriate to use the data this way.
If you designed a theoretical absorber that would give an absorption coefficient of .7 - you could cover it will FR701 and expect that the coefficient is unchanged for frequencies below 1000Hz, and diminished by a factor of .9 to .8 above that. .7 diminished by .9 leaves .63, or diminished by .8 gives .54. This, is still good absorption. Especially considering that the theoretical absorber you design will probably have the opposite curve and actually be increasing in coefficient above 1000Hz, this is probably close to ideal. How does this change if you cover it in Anchorage? Well, since Anchorage is linear across the same range of frequencies, it will just act to bring the coefficient of your theoretical absorber down from .7 to .6 or so from the get-go. Then at ranges above 1000 Hz, we still see the same auto-correct to linear (as far as we can tell).
Given the ease with which a room covered in panels can be over-damped - especially at higher frequencies - I think this is at worst not a problem, and at best, an improvement is overall liveliness. Again, do I know what I'm talking about here? No, not really. But I think this is a fairly sound argument. Keep in mind that even in small rooms where reflected sound contributes significantly to overall tone, direct sound will probably still be more significant. (We'd have to know the critical distance in your room - which will depend on the amount of absorption as well as your distance from the loudspeakers - to compare the direct and reflected sound levels - and we don't have that data and I can't find good approximations right now).
All that brings me to my question: independent of acoustics - what do you want the room to look like?