I have a H9 Ultra Stick with a new Hitec rcvr and heavy duty servos. I am getting interference with this plane occasionally and am having trouble isolating it. This is the 60-90 size in the yellow/red/blue color scheme. I have an os91fx and am running flaps and ailerons. I have isolated all the servo wires in the fuse to one side away from the rcvr and antenna. I thought I had it but I got 3 quick hits on what appeared to be the ailerons. I thought about buying twisted extensions for the ailerons to see if the problem gets better. The servos in the ailerons are S3004 Futaba. Those runs are long on that plane. I also thought about installing chokes on those wires but I am having difficulty finding any. I also thought about twisting the servo leads. They would have to be disassembled/separated then twisted and reassembled since the 3 wires are bound/cast together. Any suggestions would be appreciated.

What are you using on the throttle arm? Any metal to metal there?

I use ace glitch busters on long leads they have one to take the place of the y harness never had a problem and they are 24" long

Adding to what rustypep said about metal to metal...Muffler on solid? Rx been in a crash?Crystal in tight(72mhz)? Antenna routed properly, not doubled back( 72mhz)? Switch harness good? Tx and Rx batteries, plugs and leads in top notch condition? Long carbon fiber pushrods touching?(if used). Engine block to motor mount clearance present? Prop in acceptable balance? Tx antenna tight?

go with2.4 and no more glitches, i've been flying the same combo you have for 2 years, never had a glitch...ever