I imported a 3.2 pajero some years ago and towed my twin for two years with no problems I didn't have a sticker, but then last year someone posted on the pajero owners club about it, I asked there why we needed to and someone replied that in two wheel it put's two much pressure on the rear diff, I don't know wheather this is actual fact or not, but to be honest unless I am towing in places like the alps I don't put it in 4 wheel drive.
craig