[Christ]

As I mentioned earlier, I'd likely use a NC momentary contact above the brake, so that when you touch the brakes, it unlocks.

A more elegant/time consuming solution would be to wire the switch so that it only gets power from the 4th gear solenoid's supply, and once you're out of 4th, it unlocks. I think you'll see even more gains if you can find a way to stay fully locked as soon as you're out of first gear, though, and just unlock for EOC or slowing down. Engine braking isn't likely to save you anything anyway, since you're a more efficient driver than many, so the ability to have full lock on decel isn't as necessary as it would be for someone else.

I think the way I'd work it, if possible, would be to power the solenoid with 2/3/4 gear, and add a momentary NC switch to the brake pedal, since you're probably in neutral any time you're purposely decelerating without the brakes anyway, or in my case, EOC any time you need to slow down when it's not a reaction to some unexpected environmental change.