I have cut the beam mounts off the Lil Geo, and made a nice firewall for radial mount engines.  I carefully glued it on with 12 min. epoxy.  Yesterday, while Andy B. was ready to launch it, the engine and firwall took off!  Fortunately, he was not in the way.

There is a light coating of epoxy on the back of the firewall and obviously epoxy in the fuselage wood, but NO shreds of wood separated from either side.  The only thing I can think is that the very slow epoxy soaked WAY into the end grain wood of the fuselage, leaving almost none to provide a bond. 

I will re-epoxy it, then drill through and epoxy dowels through the firewall and well into the fuselage.  Between the main bond and the dowels, it should stay put!

Larry,
Happened to me once on an old glue joint, never on a new one though