I have a 100mm dome custom made for the 15mm Sigma lens, also the lens shade was shaved down somewhat. I am quite happy with it, I use it for almost 100% of my WA photos. I used it with my D700 in Subal housing and am now using it with the D800 in Subal housing.
DrSteve, It was an absolutely fabulous trip... shooting salmon going upstream, swimming in icebergs, playing with stellar sea lions, wolfies, octos, calving glaciers... and in the evening about 10 different scotches waiting for you! There was just that one little water temp thingy, and you just put up with it. One of our best trips ever.