Middleburn outer ring position on a dual or triple spider will give you a 54mm chainline. However, a number of smaller chainrings will not fit behind the crank arm on the 5-arm spider. A downhill middleburn ring with the notch cut out at the right place will be best.
I use a 36t middleburn standard ring and that just fits. A hardcoat ring wont fit though – too thick. I havent tried a 4-arm yet.
Middleburn chainlines work with 113mm BBs although some have said that for a 73mm shell a 115mm BB is better for the extra little clearance you may need.