J/30 Class Association Forums J/30 Forum Racing Tools and Techniques Mains with slugs ,Close the feed slot?

I'm looking at going to a Tides track on mine, but while I was following the R2AK (Race to Alaska...cool event) I found one of the boats was sponsored by http://www.mastgates.com/ . I haven't checked 'em out, yet, but folks up in the Port Townsend area seem to think they work. I'll probably try some on my Merit-25.