I have one for my 14 foot kitty. Your thoughts are right on here. There are times when it works really well (the afternoon wind on the Deschutes River in Oregon is infamous. Most people try to be camped before 2:00 PM). What I have found personally and I have a 36 inch sock, is that a shorter tether seems to be much better than the standard tether. I found the standard tether allows the sock to go where ever it wants to and sometime that is hindrance instead of help.
I now have mine on a short leash about 6 feet and tied to the front frame cross member in between the tubes. This tends to keep the sock right in front of the nose and not too deep where weird currents effect it.
Not perfect, but when it really starts howling I do find it helps. If nothing else, at least I don`t get blown back up stream. Just pull it up before entering rapids, but I expect you already figured that one out.
I like the more beer option best myself though.....