There was an article in a recent (past 12 months)issue of Model Railroader magazine, specifically about superelevation on model layouts. If my memory is any good at this point, I believe there was a table of recommended shimming of the outer rail in increments similar to what Bob N. was refering to. I keep all of my MR mags but don't know which one it was in. If I can find it I will post the info.