<span style="font-family: Times; font-size: medium; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; background-image: initial; background-repeat: initial; background-attachment: initial; -webkit-background-clip: initial; -webkit-background-origin: initial; background-color: rgb(255, 255, 255); font-family: Arial; font-size: 12px; background-position: initial initial; ">Your assumption about the engine mount might be correct.<div>
</div><div>You may need to increase the load bearing area by painting the balsa block, foam block and firewall with some epoxy to form a lightweight 'skin' to spread the load area.</div><div>
</div><div>Try running up the motor with the cowl off and check to see  if there is any movement.</div><div>
</div><div>Note the area of the previous plastic mount and try to simulate the same strength (or better).</div><div>
</div><div>Maybe some balsa sides to your front block to form a box or part box.</div><div>
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