+1 for Tek Tanks. I've not used my tank in anger yet but it looks very nice although it has just about doubled the value of my RIB!
Their brochure is worth a browse. One thing I discovered that was a surprise was that the custom tanks and possibly the others have to sit on a solid floor rather than on stringers and frames.
Looking at the sizes of the ready made tanks, Jay Wolfe and Tek Tanks appear to sell the same Osculati range of tanks. Jay Wolfe seems to do bespoke metal tanks but not plastic.
http://www.tek-tanks.com/website/wp-...SUE-3-ANNA.pdf
Edit - I think the brochure must have been written by Anna rather than being about her.