Five minutes of idle is a pretty long time. The engine will "load up" with fuel if it is allowed to idle very long. Then, when you open the carb very fast, it floods the engine and causes the glow plug to die. It sounds like you have a very good running and well tuned engine. After an extended idle, you will just have to slowly increase RPM's to keep from flooding the plug. Regarding the compression, the drop in compression is normal when the engine is hot because the cylinder has expanded more than the piston. In a lot of the newer ABC or ABN engines (no compression ring), they sometimes have no compression when hot. That's also why they won't start until cool. No compreesion to draw fuel into the engine head. I don't think you've got anything to worry about. I would suggest using less caster in your fuel. Either a blend of castor/synthetic or all synthetic. All castor in this type of engine will lead to varnish issues (i.e. a very gummed up engine).