The importer seems to have deleted the thread, but here is the relevant information from their new thread:
Barrel: 16" Melonite Barrel
Stock: Folding Stock
Stag Arms 3G Compensator (not pictured)
So, the importer is confident enough in their feedback from the CFS and their own interpretation of the law that they put the money and time in to replace the compensator instead of pinning the stock permanently open to exceed the OAL minimum.
Unless the law changes, the muzzle devices should count towards the OAL for Renegade builds.
The MRA Rock Solid Muzzle Brake would add 2.5 inches / 63.5 mm (minus the part that threads over the barrel) to the OAL, for example.
If the Renegade with a collapsed stock, a 10.5 " barrel, and a Rock Solid Muzzle device is just under the correct OAL, is creating a longer version of the brake reasonably possible for MRA, perhaps by duplicating another cavity and support ring?