rcjon, when I was assembling my Twist, I took a chance and installed my four-stroke right at the 4.25" mark. When I finally checked the c.g., it came out right at 5". It doesn't seem too tail heavy at 5". If yours is at 5", I'd go for it. And if you wreck it, I'll buy you a new one..................................just wait down by the mailbox for it.