I have a Sam James Shorty with standard baffles. I had a SJ plenum lid, but didn't like the way it fit when I started playing with it. Also, after asking lots of people, the consensus was that it would be a lot more work to fit, more work to access the engine, and not really a substantial benefit. I cut it up and used the inlets on the front of my baffles. Can't tell you too much about how good the cooling is... my new IO-370 only has 3 hours on it, so I'm still dealing with break-in temps. That said, I'm running 380/390 so far for break in, so I expect it will cool as effectively as a standard Van's cowl.