I have a flakey microswitch on my downshift, it fires on and off constantly when held down. Despite much effort at training myself, it takes me a conscious effort to do a 'fast click' (click and release in under 100ms) rather than a 'lazy click' (however long I take when I'm not thinking about it, somewhere between 150 and 200ms). As soon as the racing gets frantic, I slip back to lazy click.
I used 100ms when you first changed the debounce code and that worked perfectly in testing, but as soon as the next banger meet came up I'd double-downshifted by mistake once or twice in each of the first three races. I upped it to 150ms and for the rest of the night I only did it again a few times in ten or so more races. I upped the limit again to 200ms after that and now it's rare for it to happen at all, even when the racing's frantic.
If it was upshift I wouldn't mind, but double-downshift by mistake in a banger oval and your engine is damaged, even if you manage to avoid ending up backwards or getting tagged by the car behind.
I appreciate it's not exactly what the debounce is for, but one unintended repeat signal is as good as any other, no?
...actually, given the era we are talking about, less 
