Georg Matthews,

NO modifications except a Sullivan tail wheel bracket for 60 size to 1/4 scale planes weighing 10 to 22 pounds. My Funtana 90 is otherwise stock out of the box and is powered by a YS 1.10 using an APC 16x6 prop. It weighs 9.5 pounds (got a heavy one) and the CG is at 6 7/8 inches with NO added weights. The key to correct center of gravity is to pay attention to the manufacturer and don't use heavy servos because they are absolutely not necessary.
This plane is a blast to fly and has given me no trouble at all.