One thing to consider is location of the mount.  If you will be pressing buttons on the GPS while riding (as I do on occasion - I know, not safe), having the GPS mounted on the left handlebar is preferable to the center location of the Kawa OEM mount.  Also, the Kawa OEM center mount is lower than a handlebar mount, which necessitates taking your eyes off the road to a greater extent when looking at the GPS screen.

If you have the already installed Murph's Kevin Baker Risers, Murph's now offers a ram ball mount that easily attaches to the risers. You will also need an extension arm and a cradle for your gps. I have this setup for a TOM TOM and it works quite well.

Regarding the GPS on the top of the glove box, the process is innovative but I think this would be little hard to see when wearing a full face helmet.

One thing to consider is location of the mount.  If you will be pressing buttons on the GPS while riding (as I do on occasion - I know, not safe), having the GPS mounted on the left handlebar is preferable to the center location of the Kawa OEM mount.  Also, the Kawa OEM center mount is lower than a handlebar mount, which necessitates taking your eyes off the road to a greater extent when looking at the GPS screen.

what he said. Having the GPS close to your left hand is a big plus, and it sits higher than on other locations, which minimizes eyes-off-the-road time.

I use the adjustable one from ProjektD, it's adjustable, mounts to all 6 handlebar bolts and is sturdy.
It tilts up and down, which you will need due to glare

This plastic mount cost less than a dollar. Took all the crap off the back side. Drilled one hole in top of glove box.
Easy to reach and solid as a rock.

I agree. It's an innovative idea, but too low for my taste. Mine's on a RAM mount on the left handbar. Easy access and up high enough to see easily.

I used to have my Zumo mounted on a RAM ball on a stem mount.  It was ok but flexed a bit and I had to tighten up the stem mount every now and again.  Just recently I replaced this setup with the non-adjustable Projekt D solution and it's a lot more vibration resistance and secure.

Install here: http://banditrider.blogspot.co.nz/2012/03/newold-farkle.html

I do like that left side dash thing.  And it looks like Project D has moved to an angle adjustable version.        We went on a ride last night and used my cell phone as GPS.  Could not see the screen to save my life sitting in the map pocket of my tank bag.  Cell phone stayed on top of the bag the whole way home.  Thank god it didn't go flying (still in break in period )  But it did secure the need for the mount. 

I think i'm still aiming for the tree mount.  It just seems a cleaner install.  I think i'll even still be able to see it over my tank bag.   But I was surprised to see that not much bigger than my cell phone in wide aspect can fit there.  I don't think some of the wide GPS's will.

I used to have my Zumo mounted on a RAM ball on a stem mount.  It was ok but flexed a bit and I had to tighten up the stem mount every now and again.  Just recently I replaced this setup with the non-adjustable Projekt D solution and it's a lot more vibration resistance and secure.

I have used  my Zumo on a RAM mount off my Helibar risers since day one and never have to tighten it and have no vibration problems...

I have used  my Zumo on a RAM mount off my Helibar risers since day one and never have to tighten it and have no vibration problems...

And you probably wouldn't.  The one I had relied on a piece of rubber pushed into the steering stem hole which was then squished outwards to hold it in place by tightening the bolt - nowhere near as good as a ball bolted to something solid.  In saying all that the mount worked ok for the bike's first 70,000km...

LOL- I was thinking the same thing.
And I was also wondering why anyone would want or need TWO GPS units...

Do you run rallies. Have you ever seen serious rally/LD bikes.

 2 gps units are standard on most rally bikes with 3 units very common. And a 4th unit if it is a 2 up pair. Some are even using IPads in the tank bags.

They are used for different applications by different people. Some are strictly back up units with routes and waypoints downloaded for when/if the primary goes on the fritz. Some always have the rally HQ set as home on one unit  and it constantly reminds the rider of the amount of time and the route back to HQ so as
 not to DNF. Some show all the preselected POI's a particular rider may want on 1 and not the other.

I usually run 2 units with routes entered into both units. The primary is zoomed out to show a larger picture of the route and upcoming towns, weather etc., while the secondary is pulled in tight to show all cross roads/streets with names and also to show what the upcoming road ahead looks like, especially helpful at night in unfamiliar areas. Once you get a feel for curves and bends on the gps screen it is easier to determine entrance speeds into those curves and bends knowing (hopefully) what lies beyond. The Lowrance unit I ran a couple years ago would auto zoom at the city limits and then back out to the level I wanted it outside of those boundaries.

Just a quick abbreviated answer to your question,

John