Hi!
Touchy..???
No, No! They are very sweet running engines , very easy to set and run!
Only needs 0-5% nitro! Do not use any more nitro than 5%!
Rossi 3 glow plug works perfect (thats the original plug, though it's called Webra 3 by Webra) Enya 3 or OS 8 will work good too.
11x6, 11,5x6, 12x4, 12x5 APC prop for most sport and scale applications.
Some pictures on one of my Q-500 racers using the Webra .40 GT engine, which in practise is the same as the Webra .50.

Regards!
Jan K
Sweden