Looking for Doubble Bass Exercises (Matt Garstka)

Hello Everyone!

I'm looking for doubble bass exercises that really works.
I recently bought a lesson from Matt Garstka (drummer of Animals As Leaders), That's the first lesson I really feel have helped me out with my teqhnique. Mostly in my short, fast bursts and pollyrhythm playing though.

Now I need exercises that can help me go fast for a long period of time.
I've read about people in here that can do 16th notes at about 240bpm, that's just insane! How do you practice?

I can play 16th notes at like 150bpm for about 1-2 minutes maximum.
Please help me out here, what's the big secret?

Please share your favorite exercises! (PDF's or whatever)

Here's a clip of me recording session drums for a melodic hardcore band:http://www.youtube.com/watch?v=pJiN-Fdplgk

EDIT:
I am self taught and I've been playing drums since I was 4 years old (So it has been 15 years now).
I got my first doubble pedal when I was 17 years old, that maybe explains why I'm horrible at it!

Looking for Doubble Bass Exercises (Matt Garstka)