90+% humidity every day and it works very well for me, I guess the choice is in the wearer. OR how the bike is outfitted? Where is the rally that the original poster is going to?
And for the no fairing bike question, I do have to admit: I pulled the plexiglass off of the Rifle base two months ago, never have looked back. The theory is the more air the more cooling happens on the vest, and it works just as well with a wet T-shirt. The vest just lasts ALOT longer than a wet T.
And the comment about using warm or at least room temperature water is on target. Cold water will cool your core down too much, causing icky feelings.