Just my two cents worth...(again)...I personally feel, and have tried using the steadying sail on my GB42 on several occasions, that it is a waste of time. Meaning, by the time you sheet it in midships, tight....with 20 to 25 knots blowing abeam, you will still get a quick roll down wind, and a slightly noticeable stablize as the boat rolls back into the beam wind. But, the problem is the wave height with that much wind blowing...you are still going to roll your guts out...one is much better off picking a good weather window to make a crossing, and not go out in 20 to 25 knots of beam wind. And less then 20 knots, the sail is pretty much useless...even at anchor, it will not point you into the wind, with a beam current running.
I removed mine the first year of ownership, 11 years ago, and have never put it back up. Having sailed for 22 years in the Carribean on a REAL sailboat, soon realized that the GB42 is to heavy, and the sail is much to small...to do any real good.