Received a short "deluxe" FSB from Dinzag a few weeks ago, wanted to shoot with it a while before passing judgment.
It looks incredible. The fit and finish on it is top tier. After shooting with it (after installing properly with threadlocker, of course) it doesn't budge. I've shot a couple hundred rounds since the install, 25% of which were slugs and buckshot and it hasn't moved a bit.
My favorite feature is that the lock-down screws are hidden, whereas the Krebs style ones have the mounting hardware far too visible making it obvious that it's an add-on part. The Dinzag FSB looks like it's a part of the barrel. It's my favorite feature of the gun right now. I was iffy about the cost at first, but I will vouch this is one of the most positive cases of getting what you pay for I've experienced. It drew a lot of compliments on the local forum. I will definitely return for more parts in the future.