In the RB Lead Sheet window under "Opt", there is a drop-down listbox where you can select "Very small - 10 staves" and click OK. The chords display above the staves correctly.

If you then go back into Opt and select "Small - 6 staves" and click OK the chords also display above the staves correctly.

However, if you then select "Small - 8 staves" the display shows the chords superimposed in the bass clef of the grand staff.

Similarly, if you then select "Medium - 6 staves" the display also shows the chords superimposed in the bass clef of the grand staff.

Any setting of # staves should always put the chords above the staff.