Has anybody actually got any tech details about the amount of down force the rear spoiler generates and if so at what speed does it show its benefits, or on the other hand is it just cosmetic.

Also what are the benefits of the low level WRX version over the "Im Driving With A Coffee Table on My Boot STI Version" or visa versa.

Last but not least am I correct in assuming that having a flat underside to the car can also help with down force.

Sad I know but I need answers!