What he said. I have yet to have a nylon bolt break when it wasnt supposed to but HAVE had em break when they ARE supposed to and minimize damage in a crash. Definitely use the nylon bolts. Also the advice to cover the tailfeathers before attaching to the plane is a good one. Covering em while attached is a *****. I have always, till now, covered em on the plane and wont do that way anymore.
I built the .40 sized uproar and its a blast to fly.
ORIGINAL: majortom-RCU
The nylon bolts are more than strong enough for the task. Nylon wing retainer bolts are used on 1/4 scale and 1/3 scale planes. Steel or even aluminum would add unnecessary weight. One of the easy weight-saving tricks with most ARFs is to take out the metal bolts/screws/tee-nuts and replace them with nylon fasteners and threaded wood blocks. The only nylon fasteners I've ever had break off were on the landing gear, in situations where they were designed to release the gear to avoid damage to the fuselage.
If it were me, I'd cover the tailfeathers before gluing them to the fuselage. Saves lots of time and maneuvering.