Posted on Behalf of Dick
Thanks for the field report. I am surprised that you had trouble setting your appropriately sized Rocna as that is a function that it usually does superbly. As to the re-setting, this seems to be a problem with Rocnas which rarely, but occasionally, occurs and you are not alone in switching to a Spade.
I applaud your moving up a size as weight in the anchor pays huge dividends in keeping the boat in one place: far more benefit than any downside of adding 11 pounds to the bow.
As to swivels, not only are they contraindicated if they are stainless steel (which, to my evaluation), has no business in a ground tackle system, but they increase complexity and serve no function (see swivel area in Forum for details).
It is wise to have the end-of-chain securing rope emerge onto the deck for being able to quickly cut: make sure that the knot attaching rope (especially as you specify heavy line) to chain is executed in a fashion to not hang up on its way to the deck. I have a visible indication on the chain about 3 meters from the end to make sure I am prepared for the rope to emerge as the chain can be coming out fast in a dump.
As to a polyprop floating line, trip lines and their cousins are a complex subject, again addressed elsewhere in the forum.
My best, Dick Stevenson, s/v Alchemy