You just need to get that achievement, huh? 10GS. Thats it.
WELL SO DID I.
Okay, here it is.
Go to the Super Ultra Mega Park.
Now run backwards up the road, till you see the entrance gate thing. Run to the right side of it. Now get your object dropper and get out a ramp to climb on the white thing, and get another one to get to the tippy top. (Place markers incase you fall)
Now climb all the way to the top of the rocky hill. Jump off while spread eagling into the bottom of the park. There you go.
NOTE: Now, as you can note, i can not explain this very well.
So for a very helpfull video guide, go to youtube and search "NeverNegative 100% Pure Adrenalin". Its one of my videos. Hope this helps. Now scat your GS whores! Hahaha