Hello Andy!
Forward centerline pressure simply means that your energy should be directed forward into the opponent's centerline! This is how we control the opponent and hit everytime the slightest opening exists. It is, as Bruce Lee once said, like flowing water, finding the slightest crack and working its way through! The "center of mass" principle often taught in combat handgun training applies here as well. The most solid shots occur to the center of any mass, therefore your attacks, whenever possible, should be directed to the centerline! Control the opponent's centerline and you control the fight!
Hope that helps!

Keep Blasting!
Sifu Lamar M. Davis II
Senior Instructor
Hardcore Jeet Kune Do
Sifu@HardcoreJKD.com
JKD@windstream.net
http://www.HardcoreJKD.com
Phone (205) 296-7070 (Incoming Only)
"Hit Hard, Hit Fast, Hit First - ALWAYS!"
"The REAL future of Jeet Kune Do belongs to US, the few, the proud, the HARDCORE! Now, what are we going to do with it?" _ Sifu Lamar M. Davis II