Hi babbott78,
I am running my Hannos stock, no head shims. I am currently at about 96m above sea level. I run fuel with 15% nitro. I now use 13x9, 13.5x9, 14x6, 14x7 APC props. My pipe length averages 19” (482mm) measured from the glow plug to the first baffle in the pipe. I run a K&B 1L or OS #8 glow plug and average about 80 flights per plug with no element distortion. I am running two Hannos at the moment both have true ABC piston/sleeve assemblies.
I hope this helps!
best regards,
will