Downhill Biking is different from uphill biking. What works best for downhill won't be much good uphill.
You need to reduce the seat tube angle, get wider rims and tires, and wear motorcycle leathers with a full-face helmet, if you want to do it right.
You probably don't want to wear leather, or get wider tires, so just own up to the fact that you're not going to set a world record for downhill speed.
Like the Eagles song says : "Take it easy, take it easy, don't let the sound of your own wheels drive you crazy". SlimRider mentioned that song (above) , I agree, it's not worth getting badly injured.
http://gravitybike.com
Their message board has crashed.
Here's a video of me when I was younger, riding for downhill speed. Note: I have Kevlar Fairings ( indestructible protection against road rash), using 20x2,125 tires (95psi), and I'm wearing a winter jacket.