OK, mine is mostly done, so I'll post what I've done.
Step one, I added a 1/2" square aluminum bar the width of the shelf + about 3/4" on each side. I drilled and tapped the bar to accept screws through the PW shelf, and to accept screws that will mount brackets for GPS's etc.
I made 2 straps out of 1" x 1/8" steel strap, 11" long. They are bent at 5" from the top to match the angle of the windscreen mounting surface. At the ends of the 1/2" aluminum bar, I made small pieces that match the angle of the ends of the PW dash, and bent them down to more-or-less match the angle of the cowl. The pieces rest on the 'points' of the cowl, and help support the front of the dash.
In this picture, the bars are at full-lock. You can see the added "ear" as a shiny aluminum triangle piece.
You can see the added "ears" a little better in this photo. They butt against the 45 degree edge of the PW plate (actually, it 40-ish degrees). You can also see two bolts at the front of the plate holding the MixIt2 in place; these will be changed a little.
Finally, I made small plates that screw to the 1/2" aluminum bar that hold the GPS's, and a piece of 3" aluminum channel was re-purposed to hold the Legal Speeding radar box.
With everything in place, I can still turn the bars lock-to-lock. I can adjust the MadStad over it's full range up/down, but am some restricted as to how much angle I can put it down (it hits the 2610 bracket if UP, and eventually the screen hits the GPS's if DOWN.) I actually have more clearance when I have the Cee Baily 23" screen on, but I need to drill a couple more holes in the straps so I can move the MadStad down a little, as I don't like that windscreen with the bracket all the way up.
There are a few more pictures, and you can see all the pictures a little bigger on my Picassa
I'll post a few more after it's all painted and such.