Hiding Just 1 Bracket

Hi, I'm transcribing some 16th century counterpoint, and want to have prefatory staves for each part. With considerable work, I've managed to sort the petrucci clefs and renaissance symbols. The one thing I can't seem to do is hide the initial bracket(!) I'd like the first bracket of the page to be when the piece itself begins. I'm baffled that with a program usually very flexible with this sort of thing there is such limited scope for changing brackets without shifting how they're applied to the whole score. Can anyone help with this?

Also while I'm on the subject, is there any reason why I've had to add the petrucci clefs as symbols in text rather than musescore recognising them as clefs? The clefs already exist in musescore, surely it wouldn't be so difficult to make this change. Same with the old style noteheads — why are these not available as real noteheads?