ChoirStaff: system, staff, and measure number spacing

[Benedict Singer]

Hi all,

I've been using LilyPond for a while now, and am starting to reach the 
point where I need to tweak things slightly more than the manual makes 
clear. Specifically, I have an SATB vocal piece layed out on a 
ChoirStaff, and I'd like to tweak the following things:

1) Currently LilyPond lays out 2 systems per page, one at the top and 
one at the bottom. I'd prefer them spaced a little more evenly on the 
page (ie about the same amount of space between them as is below the 
second one).

2) I'd like a little more space between lines in the same system; I also 
suspect I'll need this when I start putting dynamics in.

3) I like the look of the ChoirStaff bracketing the parts together, but 
the problem is that the bracket collides with the measure numbers at the 
beginning of each line. This could be solved by tweaking them up a bit, 
but again, not sure how.

I started looking up how to override/tweak properties, but I'm unclear 
on things such as determining the contexts, and exactly where in the 
source file these tweaks should be placed. Even seeing how to do just 
one of these things would probably enable me to get them all. Thanks much!

Benedict