Honestly, I probably wouldn't bother in most cases, because of the second part of what I said.
and for SQL to be doing such large range scans of the table that it needs to issue read-aheads for the non-leaf levels.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability