Now this may be widely known and I may not be the first to make this discovery.
I discovered that you can control the manual output level of a slave (430 EXII in my case) from a master (580 EXII in my case) even when the master is not attached to the camera, as in fired by my el cheapo radio triggers.
That is set the 580 as Master, attached radio receiver, set 430 as Slave with OUT radio trigger attached and the 580 controls the 430
Now this is going to add some versatility to my set up, I was thinking that I really needed at least 1 more receiver that I now no longer really need.
As I said, this could well be common knowledge, although I had not come across it before