I think whichever way we go it’s going to require trust. If we only allow one entry, then some less honest people will pretend they’ve been really busy, wait until near the deadline, watch all the entries, and knock a few seconds off that. Similarly, if we allow multiple entries, then the same type of dishonest person will just re-invent the wheel with a few optimisations.
I think we’ll stick with the original rule and, like in other competitions we’ve done here, there will be nothing wrong with someone submitting an unofficial second entry with improvements. However, only their first entry will count.
At the end of the day, it’s meant to be for a bit of fun and I think most of us will play fair.