Typically a 6 pitch prop is on the boarder of 3D or not. Some guys think its a bit too fast while others are comfortable with it. I cant speak for your muffler choice although I have read posts on others using a pitts with no issues reguarding 3D. Personally I am running a 18X6W on my plane and thats the recomended prop for 3D but the W ion it takes the speed away. Like I said the prop will work, after that its soley based on how you like it for that specififc aplication.