I realize a similar post was made recently but it didn't really answer my needs.
I have a 40D with Ike housing and a 60mm macro lens. I had planned on getting a Tokina for WA, but recently I stumbled onto the 28-80mm that came with my film Rebel years ago and has never been used, so I think I'd like to shoot it for a while before I get any fancier. According to the chart I have a choice between a 6" or 8" dome. Over/under isn't important, but I am going to be staying in Okinawa for a few months so portability is desirable -- although not overriding if I am going to have buyer's remorse later. Someday I do plan on getting that Tokina or something similar.
Any insights would be welcome.
http://www.ikelite.com/web_pages/2port_canon.html
-Rob