How to hide an empty stave on the first system?

Hi, I have a vocal piece (SATB - 2 staves) where the opening bars are a single voice (bass). I want those bars set page left with a wide right margin. Insert Hframe does this for me. But I also want to hide the unused stave. I have set 'hide empty staves' and this works for line 2 but not for line 1. How can I hide the empty stave in line 1?

I have tried hiding the empty measures but the first bar line is still there and won't let me set the bracket position for the remaining stave.