About engines ripping out firewalls and hurting people, it's a terrible thing, and it should go to reinforce one of the many rules about operating these powered models. The only time anybody should be directly in front of the prop on any size engine/plane/prop is when starting the engine. Immediately after, move to behind the prop. I see people running up engines to WOT, adjusting engines at WOT, taching engines at WOT, all from in front of the prop, as if props never fail, crankshafts never fail, prop bolts never fail, engines never throw props, firewalls never fail. WHY WHY WHY do so many people insist on doing this while in front of the prop. MOVE TO BEHIND THE PROP, that way most debri will move away from you if failing. The only way to get seriously hurt when following this rule, is if you loose your balance and fall into the prop, which has happened. Sorry to rant, and it is unrelated to this thread, but do yourself a favor and follow this simple rule when handling ALL planes.
DKjens