I have the evolution .61 and am putting it in the Hanger 9 Texan I have a problem with the muffler. IF I follow there directions the stock muffler will would go through the firewall. I'm having a hard time finding another style muffler for this engine...anyone out there point me in the right direction as I don't think its a great idea to cut out a huge chunk of the firewall. I have an os .61 muffler but it doesn't match up.