I transported them in a cat-carrier aswell, small model with a pillow inside (fleece pillow). This worked very well for me; probably because they were scared from the movement and noises they barely investigated the carrier, they didn't pee neither.
I had a drive of an hour with them like this, and everything worked out ok.
I don't want to hijack your thread -but I am just curious- do people hang up waterbottles aswell? The breeder told me it wasn't necessary for a one hour drive, but from what point do you think it is? Does this depends on the duration of the trip, the chin (age?)?