Adjudicating the levitate spell - how fast?

[Halaster Blackcloak]

I'm working on something involving the levitate spell, and I'm at a loss for how fast it should cause an item to levitate. The spell description says it rises at a movement rate of 2, which is stupid because movement rates are calculated by tens of feet indoors and tens of yards outdoors. So that would mean that in a dungeon, the spell lifts an item at 20'/rd. but outdoors it would be 60'/rd. (2 x 10 yds. or 20' = 60').

To me, 20' / rd. seems slow. That's 20'/minute. That's slower than a feather falling upwards for sake of analogy. Should it be 60'/rd. though? That seems sort of fast. Then again maybe not. A helium balloon can float pretty high in one minute.

[garhkal]

20 yards/round, seems ok to me.