I think buckfevr might have hit on an interesting point. If your arrow weighs 400 grains and you are only getting 206 fps then you most certainly should not be using any mechanical head. However, if you are using an excessively heavy arrow...600 grains or more then your KE numbers may be higher.

Head to www.bowjackson.com and use his arrow weight calculator and KE calculator to help determine this.