K, so here's what I think is happening. I have the same problem as dom and keltik. Firebirds are overstable like a muther, and without crazy snap or crazy torque they are never going to flatten and glide the way other molds will. Torquing a disc over robs distance and can screw up your form, so attempting to manipulate flight with torque = stupid plan. This leaves us to consider snap...my form isn't clean at all. On a good day (with the gods smiling on me) I can break 320 with a gazelle or teebird, most days it's 280-300 if I am lucky. with this level of power I cannot honestly expect to be able to accelerate a speed nine driver (especially not one with so much HSS!) to its intended cruising velocity, ergo I will not see the distance the disc is capable of as I lack the proper technique and power. Dom and Keltik throw farther than I do but I would venture a guess that insufficient snap is still the culprit.
Solutions, Preds are good! Banshee is my weapon of choice for wind warfare though! Give one a shot and see if it works better for you. It isn't distance challenged like the whippet but it is not quite as long as the firechickens either.