Talk to Robert at MVVS, they can do any modifying. Doing engine run ups when I built this thing it took three people to hold it down and yes all our ears were ringing. I had a big reverberation problem when I first started it causing so really harsh vibrations, the engines were ringing off each other. One of the guys here had the solution. I had the props set up so that coming upon the compression the props were level. The trick was to off set one 45° to the right and one 45° to the left.