Descent Speed to high

Is it somehow possible to safely reduce the final stage descent speed (LAND_SPEED) to less than 30 cm/s ? I would like it to be 10 cm/s or less.
I can change this number to 10 cm/s but I get a warning that I should not go below 30.
What may happen if I go 10 cm/s? Will it work? I really need to land very slowly.

If your descent speed is too slow the aircraft will hover in Ground Effect…

OK, but when it hovers it does not descent? Wouldn’t autopilot automatically reduce the power to make it descent even in ground effect?

Is this the only reason for 30cm/s? Ground Effect?
My copter has long legs…

I am seriously biting my tongue here. I’ve tried to warn you. The warning you got form ArduCopter didn’t pop up just for laughs. Its a WARNING.

Its your aircraft, so feel free to do what you want. Just remember you were warned TWICE.