Basically, the site is for those interested in investing, and in particularly investments in the Aus Stock Exchange.  We have over 2000 listed companies and I want my users to be able to have threads on each listed company.  This means each company needs its own forum.  I decided catagories of A-Z was best, with a forum for each company under that.

Are you suggesting I should try a subforum style?  I haven't tried it yet, but with so many companies I think the list of subforums would get quite long.  Based purely on averages, 2000 odd companies divided by 26 letters is an awful lot of sub forums for each letter.  I'm more thinking just look and feel and ease of finding the forum they wish to view or post in.

I'm aware the forum wasn't designed for this many forums, but that is my need.  I have found that when I change the settings to Aggregate, the forum runs very smoothly.  The problem with doing this, is that my users cant browse the catagory/forum list in order to add a new post in the section they want to.  Any links to the catagories do not work.  If that could be fixed, the issue would be solved and the forum would run nicely.