I just mounted a Pelican 1520 on my FJR, using a combination of the instructions in these two posts:
Warchild mounted an aluminum plate to his Peli, and mounted that in turn to a SW-Motech rack. After problems with his rear sub-frame, Matt mounted his Peli to his OEM rear rack, which distributes the loads over more points.
In my version, I used a 12"x12"x1/8" 6061 aluminum plate as the main support. I drilled 1/4" holes into the four corners of the OEM rear rack, drilled equivalent holes in the aluminum plate, and countersunk the holes in the top of the plate. The bolts pass through the plate, then through 1/2" sections of heavy-duty fuel-line hose (like in Warchild's version), which dampens the vibrations coming through the bike. The bottom of the hose sections sit on the rack. Underneath the rack, I use large fender washers, bent slightly to conform to the bottom of the rack, and nylon-bushing locknuts. (I actually drilled two sets of holes in the plate: one set lets me mount the case with the opening to the rear, and other set lets me mount it with the opening to the left side of the bike.) One of the bolts holding the plate to the rack has a hole drilled at the bottom, and I use a small combination lock to prevent someone from removing the plate and case from the bike.
To mount the Peli to the aluminum plate, I drilled four holes in the plate 40mm in from each corner, and drilled equivalent holes in the bottom of the Peli case itself. I tapped the holes in the aluminum plate, and use button-head M8 screws from inside the case into the tapped holes, with nylon fender washers between the screw head and the case.
I mostly use the Pelican case for longer rides and/or rallies, so I wanted it to be easy to remove. To take the case off the plate, you just open the case and unscrew the four bolts. (I got some black button head bolts and some thumb-nuts to cover the holes in the bottom of the case - they work great.) To remove the plate from the bike, you unlock the one bolt, then unscrew the four bolts. I found some button caps that are close to the same color as my '05, so when the plate's off the bike I put on some smaller bolts with the bolt caps for a cleaner look.
I got the travel bag insert - a nice, heavy-duty nylon bag that fits perfectly in the 1520. For non-rally rides, I use this for extra packing space.
Purely in the interest of science, I've done some tests at FJR nominal speeds with the bag mounted so the opening is to the rear, and the case doesn't seem to affect stability of the bike to any noticeable degree.
