KLM Flying Dutchman - Untill when is it possible to cancel a special meal?

Have a special meal ordered, but am considering cancelling it as I'm hoping to be lucky for an upgrade.
Is it possible to cancel less than 24 hours before the flight, as than I can get an idea of how full the flight is according to the seats availbale at OLCI?

BTW is there any other way to see if a flight is very full (from expeiance KVS shows plenty of avilability even on very full flights).

I thought that someone posted here a short while back that they were able to do a manual override at the lounge at 5 hours before departure.

I thought that someone posted here a short while back that they were able to do a manual override at the lounge at 5 hours before departure.

Does that mean that I can ask the check in agent to cancel it, if I see that I'm high on the upgrade list? (at the gate they wouldn't allow it).

And how would you know you're 'high' on the UG list?

And how would you know you're 'high' on the UG list?

I usually (in Schipol) ask to see the list at check in, and if I see that I'm number 5 on the list, and economy is overbooked by 10 passengers, I know that I'm likely to be upgraded.