Hi,
I just got my fan and realized that because I have a slanted ceiling I need to extend the polr from the ceiling. Are there poles available? I need at least 20" from the ceiling. Will this affect how the fan works?

Yes, the poles (typically referred to as down rods) are available in varying lengths, and no, it will not affect the operation of the fan as long as you follow the directions for balancing it if it wobbles.

Lowe's and/or Home Depo type places should carry them up to 24" or 36"