I put Ultra Flos with a 20 inch case on my car to replace some Thrush Hush Turbos with a 14 inch case (very similar to the Dynomax Super Turbo). The Ultra Flos are actually quieter.

This is with 3 inch pipes, and those Thrush Hush necked down to 2.5 or less internally.

I'm very surprised at how quiet the Ultra Flos are with the long case. I had 14 inch case Ultra Flos on it before, and it was too loud to hear the motor (fresh motor), which is why I band aided it with the cheap Thrush Hush. Really, you would not think that this car has straight through mufflers with 3 inch pipes dumped at the axle now, except at WOT.