3004.89m!!!
Version 1.07 (with a speed meter added) can be found here.
Favourite tactic: whack him as hard as you can at about 45°, then as soon as he's back on the screen and the "AERIAL" bit goes red, whack him again. Repeat until the red hits run out, you should find he'll clear about 700m before he hits the ground, he's going that fast!