RE: Glow plugs... need some suggestions
is the glow plug distorting because of the run, or is it actually burning to "open".
Over 90% of the time blown glow plugs are due to one thing - a lean run. Does not matter what your mixture setting is or how cool/hot the head is when you land.
Someone described that the plane went lean after launch. If the needle is critical to set on the ground, the pipe may be set too short (you are seeing a false peak) On a piped engine, you always have to back down off of peak rpm several hundred rpm. Once in flight, the engine will "request" the extra fuel it needs to support the rpm gain - if its not there, the engine will go lean.
Distorted plugs come from being over/under compressed. The coil will be pulled out, pushed in, or slide to a side. That sort of plug failure is "good" because it tells you something about how the engine is running. Except for when the coil departs the plug and the engine eats it.
You may have a fuel foam condition occuring when the prop/engine/pipe unloads. You may not even see this condition on the ground, but in flight it manifests itself. Double check your fuel system. Unfortinately, the Tiger Demon and similar planes do not permit a "correct" fuel system install fuel foam is frequently an issue with higher performance engines.