nice plug!! hehe. What exactly are you wanting to do with your funfly? if its hovering and your short of money I would go with the wasp(you can download the plans), its designed by an aussie but it hovers very well.
The mustang and aeron style planes are all decendends of the Morris Hobbies range. After looking at the aeron I would probably reccomend that, it seems well designed and light and your existing motor would easily power it. Personally I would stay away from the pipe, they work with the smaller high reving engines but for a funfly you need the INSTANT throttle response that a standard muffler gives.