Actually, Ralph at RDTS did make a sleeve. Remove the SD can from the SD. Then slide the sleeve over the barrel and thread it onto the can threads at the base of the SD barrel. The sleeve covers the ports in the barrel. I believe he would thread the muzzle end of the sleeve so a flash hider could be installed. With the extra pressure of the sleeve covering the ports in the barrel, a standard locking piece needs to be used in the bolt group. That would give double duty with the gun.
Stay tuned, Rim Country will be doing a run of SD suppressors. Mike has inspected my CA89 SD can and says it is an exact copy of the cans they built for Todd, only the RCM cans are made from aluminum. It is my understanding that an "upgrade" will be possible for the Coharie Arms SD cans. With aluminum RCM internals replacing the stainless steel CA internals, it should reduce the weight of the CA SD can by around 1.5 lbs. I might keep the first baffle SS to use as a blast baffle. But reducing the weight by better than a pound sounds real good to me. Good luck with your "duel use" SBR project.