Kmot, just an idea here. Have you ever thought about using a larger tube for the ring? I'm thinking something like the Moki radial exhaust collector, maybe 1" ID tube. I don't think that it would make a difference performance wise, but I suppose it would produce an even deeper sound, even at high speed.

Also, with such a large tube ID, having the inlet connectors of the ring protruding a fraction of an inch inside the ring would not restrict the flow as much as with the smaller ID tube you are using now .

Radial.