ORIGINAL: rainedave
Very impressive numbers! Yeah, I would epoxy some triangle stock behind the firewall.
And, go over all glue joints; make sure you have the wing center section wrapped with glass cloth, etc.
I put a pipe on my Super Tigre .40 Bluehead. It's already turning a 10x6 at 14,111 with a stock muffler:
What is significant about a Bluehead because 14K on a stock muffler is rockin'!
The plane already has a glassed center wing, glassed firewall with triangle stock and a slather of epoxy all in the fuel hatch so I'm hoping it is enough. I'm using an 8oz Kirklands water bottle for a fuel tank. They are short and fat and exactly what I needed after I cut 3/4" off the nose of the plane when I was building it. Can't wait to fly it.