I understood your situation, thought I'd offer a suggestion on how I route mine.

Does your pull-pull criss cross or run down both sides? Most run them straight down the sides but there are people that have them cross in the fuse; it's suppose to be easier on the servo or something.

If you do cut the antenna on the rcx and don't like it you can always solder a new on. It's not hard, unless you don't know how to solder; but maybe you can get someone to do it for you.

However, if it was my plane.... I'd go with the wire under the fuse. You can see how I did it on my 4*60 that had pull-pull. Small piece of fuel tubing in the hole to prevent chaffing, a clip on the inside for stress relief and one at the far end to hold tension. I've done this on a lot of my planes.

This is just a suggestion of another possibility. I don't know if you will have probs with running the wire inside with the cables for your pull-pull.

Good luck.