I have Pelican 1550's on my F650GS. Loaded them for the CroMag rally a couple weeks ago with tent, sleeping bag, overbag (in case it got cold), clothes, booze, camp stove and misc cooking stuff, toiletries, I also had my usual bike tool kit in one of the cases. The weight handles fine down low. I may use a top case someday but strapping a drybag on the pillion is much easier. The 1550's are about the largest that would fit on the F650GS with width being the real size factor. The next size up is about 3 inches wider.