You are correct sir.
Again, try the car out on the track. The can might just have enough torque to push that final drive safely. But in general, over gearing might have a better top speed, but you might never see that speed due to lack of torque/grip/no area straight enough.
adrictan...are you racing in a club? If so, is it possible for you to make runs with a certain gearing, keep track of lap times and more importantly WRITE DOWN HOW THE CAR DRIVES. The qualitative observations you make, I believe, can be more important than the numbers.
I mean, if the car drives well and feels like it has a good amount of torque coming out of corners, and can still kick up the speed in the straights, that's what you're aiming for. However if you don't remember how a certain gearing compares to the other, you've gotten nowhere fast.
I would stick to the TT-01 gears for now. Once you figure out what you're looking for, if it needs to be taller or shorter gearing, you can look into modifying the chassis and drivetrain to get there.