Ed,
The VAM concept run at Tracy's did have a cool tube inside, which was supposed to terminate in the tailpipe and create a annulus to help draw the cooling air through. In the desire to run the muffler they, (I'm not exactly sure who), removed the tailpipe to get the muffler to fit on Tracy's test stand. I'm sure the thing was loud as hell that way since it allowed a direct path from the ports to the exit, which totally screwed the idea of muffling at all. I've got a original drawing of the idea which I'll contribute to anybody who wants to try it. The tangential on the pusher as shown would be perfect for the idea. I also have an idea for a tractor config which would work much better if someones interested. After the run at Tracy's (which was wrong and didn't prove anything) everyone lost interest in the idea which was understandable under the circumstances.
Bill Jepson