I dont think you are going to like spinning your track ball with a joystick on each side of it.
I had to push mine up in the center (or a little higher)
on the panel, to avoid as much as I can w/the trackball.
If you are aming for the panel to be a total width of 48"
I think the bottom will be too narrow to fit all that stuff in.
Keep in mind that the stick on the left will not be able to be that
close to the edge, cause you have wood underneath
to think about, plus if you mount the joy on an angle verses
straight up and down, you will need another inch or so then....
Notice my green joystick in the Pic below... With the overhang
of the panel (.5", the wood frame .75" and the wood corner piece
underneath for attaching panels, .5") this is the closest
to the edge of the panel I could put this thing.
Here is a pic of my layout that I am working on tonight as we
speak...
I had to push alot of the buttons inward becasue of the
wood along the edges that make the box, plus the 1/2" wood
that joined the pieces together... lots to consider.

Also keep in mind that if you are going for the 'dual' stick for player
1 and player 2, to keep the sticks far enough apart, that it is
still comforatable to use the buttons.
If you are playing a game of Street Fighter, you dont want your
hands rubbin against the 2nd joystick as you play.
Dave