ORIGINAL: Charlie P.
Ouch. The first thing I now do with any ARF is to epoxy 2" fiberglass reenforcement tape inside the firewall on both inside verticals, paint the tank compartment with thinned epoxy and then use an acid brush to apply Titebond II along every corner in the cabin and especially the frames and landing gear blocks/pads. Getting the glass in can be like building a ship in a bottle but It's cheap insurance. So far I've never lost a firewall, though I had one "hinge" before I started the process of adding the glass and that's why I started. Luckily, I noticed it when taxiing. "Why the heck is it pulling right so hard?" Basically, it was being retained by the tube around the throttle rod! And that was a Big Stik converted to a tail-dragger with an OS 70II Surpass on the nose, coincidentally.
Probably a good idea if you have an ARF to yank on the prop occasionally to see if there is any seperation at the firewall starting. Better you should find such flaws on the ground. I tug on every control surface as I pre-flight when I get the model assembled and ready at the field. I guess I trust CA hinges, but I still check.
Those are great ideas for most models.
The inside of the firewall on this Skybolt ARF doesn't have anything behind the top of the firewall but white foam.
All good ideas for sure, and you might also think about adding a layer of real plywood over the front layer of Liteply. Even thin "real plywood" is made of decently strong wood and glue. And it stands up to crushing way better than Liteply. And won't add much weight. I've started doing that on all the ARFs I care about. Like the H9 Corsair I'm about finished. I plan on having all my airplanes long enough to wear out an engine or two, and don't plan on wearing out the firewall before the engines.