How long should a CP Pro tail boom be?

[slikrx]

If you've been reading this thread : (Click for LINK) (http://www.helifreak.com/viewtopic.php?t=32309)

you know I'm making a CPP rpetty much from scratch.

I purchased a 24 inch long piece of 5mm CF tubing for the tail:

http://i48.photobucket.com/albums/f206/slikrx/cooltailboom.jpg

When I did the DD mod on my "stock" CPP, I did like they suggested on bladecprepair.com and shortened my boom by ~1". I have had my main rotor slap my tail rotor. Not good.

I know that a longer boom will move the CG aft, and that it will (slightly) increase weight. BUT, a longer boom should increase the authority and reduce stress on, the tail motor. (longer lever arm, so more torque, less force)

Is there some "magic length/ratio" I need to use?

Any ideas?

[Buzzkill]

I doubt +/- 1" would really make that much of a difference would it? What prop are you running? I could cut mytail about 1-1 1/2" without risk of rotor strike.