The size of the tail on a racer actually isn't nearly as important as the drag from it on the straightaways and sometimes more importantly the induced drag created when it has extra work to do. It'll be doing that work in the turns. Speed lost in the turns costs you every foot of the next straight. And the speed can be lost almost instantly compared to how long it takes to get back.

And what BMatthews just mentioned about the CG having to be carried farther forward for smaller tails applies twofold when that tail tries to pitch that forward CG around a turn.

When you move the CG forward from it's most favorable location, it begins to LITERALLY increase the weight the wing has to carry. It actually doesn't change the weight of the airplane, but it does create an increase in the moment (a moment is a force times a lever arm) the tail has to balance. And the tail does it by creating more negative lift. And the wing has to actually carry that extra lift and support that increased moment. So the airplane flies as if it were heavier, because the wing is truly having to carry more weight. And what happens in that situation? Even more drag is produced. Appreciably more. And what happens in the turns when centrifugal force multiplies the affect of the misplaced cg? More lift required, and more drag created.

You do not want to move the CG forward from it's most favorable position on a racing airplane. And if you reduce the size of the tail from it's optimum for carrying that sensibly placed CG, you do yet another thing that hurts a racer far more than it hurts your everyday model. For a smaller tail to produce the same pitching effects a larger one produces, the smaller one creates disproportionately more induced drag doing it.

How do pylon racers work out the best size tail?

They plan on the CG being as far back as possible. That doesn't mean so far back that the airplane is too hard to fly. It means they don't move it forward for any but the most important reasons. And there aren't any usually. And then they size to tail to match. What is a good way to do that? The CG locator application at geistware.com is an excellent tool to do just that.

When the CG is NOT forward, the tail is more efficient. The elevator is too. And that means the elevator deflection is less, not more. And less deflection means less induced drag, almost always.

The really hot pylon designers look up the airfoil's CP and consider that for their start point. And they usually try to figure that location based on the AOA of the wing in the turns. And then redraw and redraw as they compromise and fiddle and twiddle. And when the sucker starts flying they look very hard at how much their new killer slows in the turns. Because that's usually where the races are won.