My post refered to a muffler solution for the Rossi side exhaust engines.

As for the Rear exhaust engine...

RE options are limited to a standard header/pipe type of setup. Jett used this type of pipe setup for the FIRE engines, but no spring is required... the header/pipe combination is welded, and just a solid pipe mount is required.

You may be able to use Jett's RE tuned muffler. This depends on the exhaust diameter. Pictured here (partially) on the Fan-Jett 50. Worth dropping Dub an email with a question.

I hope this is helpful.

Bob Brassell