Here's what I'm doing, leaving June 5th for a 3-4 week x-country, using the $30 Hart stackable medium tool box. I have the MP3 Rack, but I'm sure it'll work with any rack. Bolted to the rack it is waterproof, lockable and stackable. I had the smaller box, which I will use for easy access to maps and camera equipment, coffee making gear etc. The great part is after the trip I unbolt it and have another tool box. If you purchase an expensive top case the you'll only use when you do long trips or you could leave it on but we have the F6B because we didn't want a top case. Anyway, just an option