I recently obtained a Ruger 9mm PC Charger...
The short answer is that you cannot register it as an SBR because of Maryland's laws - thus your only options are to remove the brace, add a stock and muzzle device to make minimum length requirements (big money!), use a brace that's "ok" (after removing all accessories), or turn in the gun.
Said another way the current proposed regulations unfairly financially burdens Maryland residents.
Be sure to post that when ATF opens up their latest missive for comments. I plan to do so. Not to mention go on at length about spending hard earned money in good faith, changing rules with little or no analysis as to end user costs, etc.
D.