[Replicant]

There is a search filter that can be added to the search string

"channel":[19] which would specify only threads inside the forum with nodeid 19. Also, I believe it is an array, so you could actually use javascript to build the search string based on selections with check boxes or radio buttons, maybe even set a cookie to remember the selection. I don't have time to write the code anytime soon though.

This setting is also available in the sitebuilder widget editor in simple mode, if you are just wanting threads from http://www.t5forums.com/vs to show on that page, edit the search widget on that page.