I don't love it. I am a geek and live with my garmin GPS data. I'd hate to give it up for the ride. Just guessing how long it will take and attempting to hit that that is OK. But I'd rather guess, then try to beat it.

i can't imagine slowing down just to match my guess either.

Here's a notion: We want people to accurately estimate their times, and then go as hard as they can. Right?

Because of the staggered start, everyone, if they estimated perfectly, would arrive at exactly the same time.

How about we take the average of everyone's arrival times. The winner would be the closest to that time.

There's no way to know in advance exactly what it will be. But it should represent the combined wisdom of the group.

It also gives everyone the impetus to estimate their time accurately.

you could also award
flat out fastest
worst personal estimate (rubber duck award)
closest personal estimate.

I don't have to remove my computer for any of these!