Allen may want to comment on this, but because there's a fairly shallow-depth lip on both sides in the vertical orientation to allow for drop-in into a ceiling grid, the horizontally-oriented diffuser won't stand on its own in a standalone configuration (like the one I employ atop my dining table or atop speaker stands in my bedroom system) absent attachment via adhesive to, say, a plywood back with protruding frame behind it to support it.
Yes, I planned on adding a backer, in fact plan on installing them (including backers) on movable stands. If they are similar to the GIKs, then the lip can be trimmed off. My concern is performance. If I understand correctly, the GIK Gridfusors are already a paired/inverted set of QRDs, formed into one assembly. So they are recommended not to be placed as I described above.
The SRLs are slightly different on each end, so just wondering...