well not making one but i need to modify one, i need to know what length the links need to be... does half the width of the frame sound correct? 
my inner width of the frame is 36" so i figured 18" ???
i got the watts link from speedway.com
      
                        
                      
                             
      
            
            
        from what ive seen, and dont hate by this, by Mike White, is that the bars should be a couple inches longer than half the width of the frame. that allows for more suspension travel. 
heres a good pic off of his website
also, i've never really worked with one before, but ive done a bit of reading on them, and that is how i would set one up. also, be sure that the bars are parallel to the ground at ride height.