My buddy sent me a picture of his muffler and it had 10 holes that I would guess about .125" in diameter. I made 9 holes .160", I don't know why I did it this way, I just did what I thought looked right. I thought the only purpose was to get the exhaust out of the cowl and didn't think it mattered much about the holes. Anyway...I should have it about ready to fly this weekend but the weather looks pretty grim. I don't plan to test fly until a nice day but I'll let you know how it goes.

David