I have a brace on mine. If or when the brace option goes out the door, I will SBS it. I actually bought a mag fed Remington 870 Tac14 right as Remington went bankrupt and mags dried up.
I love compact shotguns and think they are very under rated. I bought a Remington 870 Special Field to do an SBS on. It has the factory 3-round mag tube, so it is a bit shorter that the 4- mag tube. So it can be a bit smaller. I need to file a Form1 and get going. But I always find something else to splurge my $200 on.