engine rpm , head speed , gear ratio

[vandelescrow]

I am planning to put the YS91SR Long Stroke engine in a Raptor 90 3D and wondering if anyone curently has this engine, what does the manual say the optimum rpm is?

This way when I order the heli I can also order the gears needed. The standard gears that come with this heli is a gear ratio of 8.27:1

Also for a 90 size heli, what is the target head speed? I currently fly 50's so I'm delving into an unexplored arena for me.

Thanks in advance