Resizable=1,1,1,0
Pos=0,0
Size=800,70 (I had to change this from the original, as MacMaster's just seems in error [he had it at 300]. I use 800 so it adjusts to the smallest screen possible. Personally I use it at 1920. The screenshot is from 1280-ish, just for display size.)

Obviously, at one end I'm using the %I mask (Pos=352,14 / Size=70,11), and at the other the %J (Pos=697,14 / Size=70,11), with an alignment of 1 to right-justify). The %R and %L are centred at Pos=375,19.
The trouble, as the screenshot shows, is that %J seems to think it "owns" the space from the middle of the bar to it's end... thus cutting off the top of "Byrne The Knee Plays", though "David" is fine. I can solve this by just placing %R and %L two pixels lower at 21 (from 19), but that still means I can't use anything else in the middle of the top line (it gets overwritten). Why is this happening? By my reckoning %J Pos=697,14 Size=70 (Resizable=1,0,1,0) is necessary to place it at the far right... if I go further than that, it's misplaced. Surely Size=70 shouldn't create a field large enough to overwrite the Artist/Album text?
Do I have the Resizable wrong for that placement, or what?