The whole "make the wing longer" vs. "make the wing smaller" thing depends on what you're starting with, and just how fast you're going.

When designing SSC combat planes, we discovered that more wing area and a longer span made the planes go faster. Faster here meant a top speed around 55-60mph. Obviously, the lighter wing loading was allowing a lower AOA and getting us to a better place on the L/D curve.

On the other hand, as I understand it, one of the reasons for cutting down a wing on a full scale racer is because the origional warbird was designed for performance at a combat weight that's a lot higher than the weight of the stripped down "a flew laps around the pylons" configuration. Less weight means that they could chop wingarea without causing too high an AOA. Someone correct me if I'm wrong on this last bit, but I do know that the "combat weight" of a P-51 is quite a bit higher than the weight of a P-51 with out guns, ammo, armor plate and drop tanks...

Anyway, when modifying a model to go faster, you need to know, did the origional designer put in too much wing, not enough wing, or just the right amount of wing for the speed you want to go. I could see a situation where adding wing makes you go slower and chopping wing makes you go slower, if the origional designer did a good job.