I thought the 393 had a double bow roller? The 411 does, and since they are so similar, you may be able to adapt a 411 double roller. A double roller is nice, but not essential - I keep a 66lbs Manson Sumpreme, and 35lb CQR mounted. My third anchor is a Guardian (think it is a G37) which I keep broken-down in the aft lazarette in it's custom bag, along the tools to assemble. The CQR / Guardian's 250' of chain/braid rode sit in a plastic drum in the anchor locker. Drilled a bunch of 1/2 holes in the bottom of the barrel to drain water. There is no need to build a separator.
I bought the beneteau, in part based on the excellent ground tackle design. Two guys could get down into that anchor locker. An oversized horizontal windlass recessed inside, and that beefy double bow roller. And the whole thing doubles as a crash cell.