How important is a deadline for an open post-doc position?
Certainly we can construct scenarios where being late with an application would hurt you, but whether or not it actually does will probably strongly depend on the pool of applicants available.

In all likelihood the soft deadline means "we won't start considering applications until Nov. 24th, but after that point in time we might select and hire someone". If you want to guarantee that you're given a fair assessment it would be wise to have your application in as soon as possible.

If this is really a match-made-in-heaven, and you're confident that you're just as appealing to them as they are to you, it might be worthwhile to send along your CV and a short cover letter explaining why you are really ideal for this position and giving a specific date by which you'll have a complete application submitted.

Note that they're probably only waiting a couple of weeks at most for any stragglers. Don't plan on applying in January.