Generally, I'm against a multiple
anchor deployment, as if you start to drag, you can run into some serious complications, especially if the different
rodes get twisted or fouled.
The real issue I have with the
Fortress anchors, is that being made of a lightweight aluminum alloy, once they break free, they will plane and not reset if they have any momentum.
The first two
anchor rodes sound quite sufficient, but the third one is a bit light. I use 30' of 5/16" G4 and 200' of 5/8" nylon for my primary
rode, but my boat is both smaller, less massive (about a third the mass) and offers considerably less windage than yours.
The really important part of any storm survival setup is chafe protection and having it setup properly...even the heaviest
anchor line will fail if it chafes. I recommend using something that absorbs water, rather than something that is waterproof for chafe protection. Heavy canvas, denim or something like that is very good chafe protection. The reason for this recommendation is that another source of failure in heavy storms is the nylon
line failing due to melting from internal friction. Denim, canvas and the like, while heavy enough to give a lot of chafe protection, allow the nylon
line to get soaked and helps prevent failure from internal friction.
As for the setup you've described... it would be very vulnerable if the wind shifts 180 degrees IMHO, as the
rodes would almost inevitably wrap the
rodes around each other. Also, it doesn't really make sense to have the two
danforths on a shorter scope, unless it was all chain—which it isn't in your case.
You don't say what the draft on your boat is, or what area of the world you're sailing in. Most cats have a fairly shallow draft, like my trimaran, and a better idea for hurricane survival is to take advantage of the shallow draft and hide the boat in a shallow canal or river, and use
lines tied to large trees, bridge abutments, and things like that...which are far more sturdy and reliable than any
anchor planted in mud or sand.
The real advantage of using a shallow river, canal or bay as a hurricane refuge, is you can often find one where you can get a fair amount of protection from the wind, and limit the direction the wind has a open shot at your boat...and then are able to secure the boat to resist the limited wind approaches more strongly. Also, picking the location allows you to limit the storm surge and how much fetch the wind has to build wave height to throw at your boat.
