I've run W9 covers on w2,w5 and the w9s with no
issues(all reverse lip ones)
Well there are specific valve covers and gaskets made for w9 heads. There not the same as a factory cover or gasket.
I thought it was just that you had to run a wide style valve cover / reverse lip, and then trim the lip and the gasket to clear the valve springs.
Do you have a link to the W9 specific ones? I couldn't come up with anything on eBay, Jeg's, Summit, Mancini Racing...