G'day Kirk, Jotun, which I last bought in Malaysia some years ago was banned in Oz due to it containing tributyl tin. If your Jotun was applied in Oz, it will probably be CUO based and if the biocide is the same as Transocean, I would take the chance on the medium also being the same and I would not worry with a barrier coat.
Either way, Transocean will not honour any guarantee unless it overcoats either itself, or an approved barrier coat. I wish I could be of more help. If there is a compatibility issue it could be a costly exercise.
"if at first you don't succeed....Redefine success"!