pwm at 31 Khz, on a mega 1280

From what i've read, i should leave timer 0 alone as that's the one that affects the milli's timing,

timer 1 affects some other importiant stuff, and one of the timers is used by the servo lib. so i need to avoid them,

Thinking timer 4 is best??
works pins 6, 7 and 8,

So adding :

TCCR4B = TCCR4B 0b11111000 | 0x01

somewhere sets timer 5 to 31.250Khz?

Any other code i need to add? and do i add it in the setup part?