We looked hard at active fins for Swan Song but when pressed by questions few manufactures would give us the answer's that we needed to climb over the $50K admission fee. Swan Song at 95,000 lb with a beam of 13' draft of 6' with our roll period 4.1 seconds and a speed of 5 kts in the rough stuff...i.e. 12-15 ft seas would need fins that are so big that they would slow the boat considerably and also be very difficult to fit. If the boat needed to be slowed to 4 kts or less then we would have virtually zero stabilization from them. If I gave them the parameter of 7 kts of speed then the roll reduction would be better. I can't imagine quartering into head seas of 15' at 7kts!! Good way to break the boat. Slow and easy. So what we see is that active fins need good water flow and as you slow down they start working harder. Eventually they become basically non-effective. No different that a rudder. Small rudder = fast boat. Large rudder = slow boat. Paravanes are much less affected by speed as they are only designed for slow boats. Ever see a shrimper planning?? So their very nature relegate them to a small segment of the market but the one in which our trawlers live. Similarly the roll tanks are not for 30 kts boats as the roll period of a panning boat on plane isn't the same as when is displacement mode. Roll tanks work on boats that have the same roll period from 0 kts up to there top end so again they tend to be much like fishing boats and our trawlers. When these boats with active fins that might have worked for many miles of coastal cruising suddenly go to make a long passage to things invariably happen. 1. They slow down to conserve fuel so are running much slower than they typically do..ie the fins need to work much harder putting more stress into the system. 2. The seas are rougher for a longer period of time so that the duty cycle and work required go up dramatically. The higher stress level is present for a longer time so issues will develop and bits will break. Both of these conditions lead to failures of one type or another. As John says a failure of an item, no matter how good the customer support is, while you are at sea isn't good. If fact it can be very very bad depending on the item. As you know we opted for the anti-roll tank vs. the paravanes. If we needed a back-up, which I can't think of why would, it would be paravanes not fins. Given that we have no moving parts, no maintenance items, the fluid used is water and that the tank just sits there working 24/7 is a benefit that none of the other systems have. At sea simplicity wins hands down over hundreds of parts that must work together in the case of fins and 10's of parts that have points of rigging failure in vanes. We noted that Milt reported rolls of 20 degrees.....we hope this is a bit more than they are having. We experience rolls of no more that 5 degrees normally in 6-8' seas and have yet to have a roll more than 10 degrees even in the 12-15 ft seas. If you recall we experienced seas of this size a couple of months bad in the passage from Bequia to St Vincent. Our non-stop 90 hour 500 miles passage south to Venezuela last year was in occasional 8-12 ft beam seas and still no rolls beyond 10 degrees. We do, as any other boat, pitch when going up or down wave and fall thru big waves that can't support us...i.e. no back side....uggghhhh. However barring that life about isn't as much of a hand hold here, there and everywhere. Generally we can make it from the galley where a cup of coffee is made in the microwave, get the cream from the fridge without anything coming out and go back up to the pilothouse without any strain. If someone has the money I'd venture to put the other two systems, fins and vanes, on Swan Song and go to sea to make a definitive test. Till then I'll stick with what we have as I know the short comings of the other to systems from my own personally experiences and those of other. Hey, Milt already has the two most expensive systems....maybe it would be better if he put on an anti roll tank ;-) Then the test would be more meaningful on a contemporary designed passagemaking boat! As always YMMV..... Cheers Dave & Nancy Swan Song Roughwater 58 Caribbean Cruise '07