Greetings.
My experience with Slimeline mufflers is that they're defective in design. I brought this up to the principals at the Toledo show 2 years ago and was given a lame excuse for the fact I would have to cut notches in the stingers or chop some clearance in the engine mount so the muffler mounting face would meet up with the exhaust flange of the engine. This isn't true of Bisson or J'Tec mufflers. The stinger welds of both the Bisson and Slimeline will fracture when the model" noses in", so I cut them off to about 2 inches and install neoprene or silicone tubing for extensions. Some guys use vinyl and it works just as well but requires occasional replacement.
Regards,
DrGO