This is a link to a guy building a big cub [link=http://spadworld.net/forum/viewtopic.php?t=17208]CLICKY[/link]

It is doable and the conversion of the weedwacker is well documented on the net. Unless you are a scale purist I might extend the nose about 3 inches to help with the CG.

At the end of the day it will cost you more than a traditional trainer but seeing your own work flying is always special.