I have a Sundowner with the water tank under the gooseneck. And if you read
the instructions that come with the trailer, the instructions say to fill
the water tank to the top. You either ride with a full tank or an empty
one, to prevent the problem that you are talking about with the unbaffled
water. We fill our tank to the top and we open the spiggot just before we
leave the grounds of any ride.