I did a boo boo with mine awhile back. Basically landed it somewhat hard out of a flat spin.

The motor mount center punched the firewall cleanly. The cowling wasn't even messed up, but the firewall had a neat, clean hole completely through it. It is made of two layers of LITEPLY. No lie.

LitePly is quite variable in quality. Firewalls ain't where you'd want to use it in a manufacturing environment with workers who have no understanding of wood selection.

If I put together another one of these ARFs, I'll probably layer some AirPly to take the compression of the motor mount bolts on the inside, and to take the stress risers around the motormount/firewall line.

I autopsyed another plane yesterday that had a LitePly firewall. We'd noticed the engine/mount flexing under the starter load and were planning to check that firewall. Got the opportunity to see it close up. It was crap LitePly. $300 ARF with two layers of crap liteply.