First and foremost, don't do the first range checks with a PCM receiver. EVER!! If there are electrical issues present the PCM receiver may mask them until they become bad enough for the receiver to failsafe itself into the ground. It's happend too many times that way. ALWAYS do your first range checks with a standard receiver to determine that there are no issues present, then change to the PCM.

Running the receiver antenna through a plastic tube through the fuselage is a pretty common method of directing the antenna through the fuselage to where you want it to go and support it at the same time. THat's a non-issue. What is often a concern is running that same antenna (in or out of a tube) if it places the antenna wire in close proximity or between the tail servo leads. You want to keep the antenna as far as possible from the servo leads whenever you can. That's why so many people run the antenna externally on the top or the bottom of the fuselage.

I've often had an antenna wire running right down the middle between a pair of batteries without any problems but the final range checks will always be the answer to that one.