Hey Bob P the next step is to soft mount the engine with wellnuts - Lowes sells a wellnut that has the exact thread size for zdz 40 - simply open up the holes already in firewall to accept the wellnuts - this isolates the engine from airplane with rubber = vibration is a little less but you get rid of that horrible guitar noise just above idle, creates a soft sound throughout power curve. the wellnuts cost $1.75 for a set. If you had a wide body pattern plane with large firewall you could attach an oversized carbon fiber plate to back of engine then attach the wellnuts to the outer corners of plate through firewall near where it meets the airplane - this setup would rival a hydemount without the weight and too much rocking for the cost of plate and wellnuts - maybe $18 someone said if its not tried its unknown?