It was a fairly straightforward process to mate the 4ft piano hinges to the oak trim on the MMG's, with the only modification to the hinge necessary being to 'clearance' the openings for the screws that mount the trim back onto the speaker once the hinge is installed.
I did learn the hard way that you cannot mount the speakers too close to a front (outside) drywall corner, as the weight of the speakers will result in the drywall tape popping along the seam (DOH!)
Moving them in (back) 1 stud from being flush with the opening worked in my case, and still yielded a good 4ft placement from the back wall.
The alignment of the hinges to the oak trim is fairly important, as they need to be straight enough to allow the speakers to swing smoothly throughout the 90º sweep of the hinge once mounted. A pencil line along the trim could do the trick. Since the trim is oak, you do need to drill small pilot holes for the screws too!
Also, I chose the wood screws so they would seat flush into the hole and allow the hinge to open all the way up. Otherwise, they would automatically hit their limit with a bit of 'toe in' (not necessarily a bad thing for Maggies).