I think it will depend on the kind of muffler you have. I have the Keleo P-51 pipes on mine which does require cutting the cowl but the look and sound is worth it. A guy I know has the DA-50 in his and there was no cutting on the sides of the cowl. I don't know what kind of muffler he had but I'll pay attention the next time I see the plane. The key here is the rear induction carbs on the DA-50. 3W -55i and the Revolution. I happen to have the 3W -55i but wish I had the DA-50 instead. The DA is a much better fit as the entire engine and carb is out in front of the fire wall. The carb on the 3W goes through the firewall and in the fuselage which required a lot of cutting of the firewall and carb adjusting is a real pain. Once installed and the engine dialed in flies the plane fine.
K.O.