STS, early this year, around the opening of Gulfstream, longtime handicapper and writer, Dick Powell wrote a column that had a great deal to say about rail placement. This was rail placement particular to Gulfstream. He had kept records throughout last year's meet, and maybe prior, as well. I'm not sure.
Anyway, if I recall correctly, he indicated that the rail, when placed at 0-12 feet out would favor inside speed horses. When the rail was set outward at 82-84 feet, this was a time when horses racing wide and closing were more favorable.
I found it all interesting and helpful.
www.TSN may still have a copy of his column.