IMO there's a lot of wisdom to be gained from all the opinions above, though not all of it necessarily applies to the majority of multi-hulls, the majority of the time, nor does it apply (from what I understand, without inside knowledge) to the Leopard incident.
The 'anti-self tailing/cam cleat only' crowd has a great point - WHEN when the boat is being raced and/or pushed very hard. But the reality is that most performance multihulls spend most of their offshore passages (non-racing/deliveries) significantly underpowered, sailing at 75%-85% of their potential, which makes most of these 'hard and fast rules' about cam cleats and all a moot point.
On Gunboats, it seems you spend spend most of our time offshore trying to slow down, rather than speed up (except in very light wind) and have never been so powered up that we felt like capsize or even flying a hull was anywhere near a possibility. It would take double or more the apparent wind to bring us to the point of 'sheet in hand' sort of sailing, and if we got there, we would decide we were pushing unnecessarily hard for being on a delivery passage, and subsequently reduce sail. This is backed up by the fact that all of my other multi-hull captain/friends tend to average 250-300 mile days on delivery, which as you know is well slower than potential.
If you are sailing hard enough that you're concerned about a 25% sudden increase increase in velocity, sure - skip the self-tailer and turn the autopilot off. OR just reduce sail and slow the boat down. Sounds like that's what happened on Leopard. If you're so underpowered that you're only making ~7 knots on a performance cat, then chances are that a wind event strong/sudden enough to capsize you won't be avoided with any sheet-management system, be it an 'Upside-Up' type system, or a cam-cleat+manual steering tactic.
But who knows - never met a sailor yet who's seen everything there is to see at sea..
Absolutely agree with your comments above. The number suggest Leopard saw something like a 3X increase in wind speed (25 knots to the about 75 knots it would take to put them over with the stated sail combination - if my math is correct). The one bit I don't know nearly enough about is what the upside up system can and can't handle... but the theory that it might have been able to deal with it (a safety redundancy) is interesting enough that I want to learn more as we are looking at going back to an offshore cruising performance cat.
The other thought that occurs is that as much as I hate hydraulics and want to keep the new boat simple as possible, hydraulics are maybe unique (?) in that "dump" buttons could be located in multiple areas of the boat.
So much to learn from when we last did this so many decades ago.
Tis true - some of the GBs offer as many as 6 trim stations which house both 'Main In & Main Out' control buttons. These can be found on either side of the interior helm, on either side of the forward cockpit, plus one next to each of the aft-mounted winches (near the transom - but not found on all GB's). In addition, there are two very large/visible/accessible 'DUMP' buttons that will blow the ram in an emergency situation.
-very convenient for trimming from any position around the boat
-Less risk of someone mishandling the mainsheet - ie opening the wrong clutch or unwrapping the wrong winch in a busy cockpit
-Since the load is massive on the main, there is a safety factor in not having to handle that line manually. Not so critical for pro crew maybe, but if you're pitching these things to owner/operators...
-I'm still not entirely comfortable with relying on a Hydraulic system to control my mainsheet - especially on a performance cat for obvious reasons. There's something to say about having a manual winch and line in front of you
-The ease and trim are a bit slow - certainly slower than the average winch would be
-The 15' hydraulic ram & block add a tremendous amount of weight and complexity inside the boom, and often make life difficult when trying to manipulate reefing lines, outhauls, etc through the cavity
-I've never had to use the emergency dump button, but imagine that the release might be violent enough to tear the mainsail as it flogged into the spreaders. With a mainsheet on a winch, you could dump very quickly whilst still maintaining enough control to lock it when you feel the power spill (hopefully before blowing up your mainsail, which would be its own nightmare to recover on a boat like that)
-There has been one report of in-boom hydraulic ram leaking all its fluid out during an offshore passage, and it turns out, unsurprisingly, that its pretty difficult to jerry-rig a main sheet on a boom which was never designed to couple with a standard mainsheet.