im running the curtis muscle pipe on my ergo 60....great pipe...low noise(blows the loud tuned pipe theory out the window)great performance and doesnt make the needles any harder to set.....intructions call for a gap of 1/8 inch between the header and the pipe....thats where i have mine and works flawless...using it on the OS50 im not sure if these measurments will still hold true....you might have to experment a little.....also i think curtis has a ask curtis section on his website...you might try looking up anything to do with the 50...he might have an answer for you......hope this helps