Do you have all your RX stuff--like switches, servos, batteries at least 12" or 15" away from your ignition system?

On one of my planes, I had to seperate everything by almost 18" to stop the RF problem.

Try routing your antenna down the side of the fuse and then put a 90 degree bend in it and run it along the LE of the stab. For some reason, putting a bend in the last 25% of the antenna can help out with interference problems.

If you want to run the last part of the antenna along the LE of the stab--just secure it with a few 1" wide strips of monokote or ultracote. Iron the strips on the bottom first and then route the antenna. Fold the strips up and over the LE of the stab and tack them down with an iron. That holds the antenna really nicely.