I've never done that.
Usually you connect a max. of two cabs. Lets assume each one has 16Ohms, you'll end up with a load of 8Ohms from the amps POV.

Having four amps with 8Ohms each, you could connect two in series (which is then 8+8=16Ohms) and then those two daisy chained cabs in parallel again (back to 8Ohms).
I don't see any way to connect all four directly to the amp, though.

See our musicians thread here: http://imotorhead.com/forums/ubbthreads.php?ubb=showflat&Number=3231&gonew=1#UNREAD
Maybe someone there has another idea.