I make aluminum pipes for my YS engines, this is just in case I put one in the ground it doesn't tear up the threads in the cylinder head like it will with the stock threaded (steel) exhaust pipe.
So I was wondering does it matter how long, or short I make them in regards to the changing the performance of the engine? Any additional information would be greatly appreciated.

I don’t think really matters that much with a 4 stoke. The racing stack looks like the shortest. The straight stack is 1.5” in length. https://www.centralhobbies.com/cat3....t=4&subcat=122