That is peak RPM, once you find peak on your tach, back it down 300-400 rpm. Since you are using a standard tank, you may want to back it down 500 rpm.

I am convinced that motor develops its best power right around 14 - 14.5k rpm. Use a prop that peaks in that range and back it off.

I like the K&B HP glow plugs, or McCoy #9's.

Also, I don't know if its legal for that class, but I remove the baffle from the muffler, and after breakin, remove the .008" head shim. For a while, I had just backed it down to a .004 shim, but now don't use a shim at all. Since the motor only has 4 head bolts, it is important that you carefully snug the head bolts up evenly or you won't get a good seal (the shim does help with that).