If the suppressor has multiple pieces that can unscrew from each other and do not have reverse threads to keep the suppressor together while removing it from the barrel, I wouldn't be sticking it under a hand guard.
9.5-10.5" seemed to be the sweet spot for .300 Blk, when I was researching.
I went for a 9.5" barrel and 6" hand guard. The hand guard could be longer, and still not cover the muzzle threads or suppressor; but I usually only care about covering the gas block, and the 6" hand guard did that just fine (while saving weight).
With a SilencerCo Harvester .300 attached, my overall barrel length is 17.75". ...Still reasonably short, and plenty handy.
Based on what I've read about the Rebel SOS-Hunter, I wouldn't spend my money on one. I wouldn't even pay for the tax stamp on one that was FREE.
Low quality. Poor fit and finish. And short lifespan.
I wouldn't go there.
Pony up a couple hundred dollars more, and you can get something decent.