Yeah you need a special slotted nut tool, or some kind of custom tool. What you do is put the tool on the nut, then insert an allen key down the centre to hold the strut still while you use a spanner on the tool to undo the bolt. Some people get a suitable socket, then grind 2 flats either side so they can get a spanner on it for example.
I've heard if you jack it up get some spring compressors on it, it takes the load off the nut and makes it a little easier to undo, but not sure how true that is.
