When you go to paizo.com/pathfinderRPG, clicking on the Messageboard link takes you to the forums as expected. However, they're already loaded if you scroll beneath the product listing. If you put in some javascript to just hide the rest of the page content to shift the forum up and change the subnav to load the messageboard links, I'd think that'd save you a lot of duplicated work. I, for one, go to the above paizo/PFRPG as a shortcut to get to the PFRPG messageboards and notice that forums already load when the product section was a bit slow loading one day. That, or stop loading the message boards on the Pathfinder url and just maintain the Messageboard link as is.
Another tip: when clicking on the number of new posts on a thread, do some detection. For small updates (>=~5) display them inline with an inline reply option as well as an option to go to the thread page. This should also save request overhead for frequent visitors and responders.