Rated 5 out of 5 stars
For Firefox 5 you just need to edit the install.rdf (inside the xpi file) like it is often possible. You can open it with an unpacker and repack it after. It is easy, search in the net for an how-to if it is unclear.Set maxVersion to 5.0It works on my machine, I just did it.
Easy DragToGo is one of my favorite Add-Ons, it is so useful if you use the mouse in Firefox, very handy.