Table-Rout Long Workpieces "Crown Down"
When molding long workpieces on a router table, the workpiece must be held flat against the table and fence in order for the router bit to cut a consistent, smooth profile. Even with the help of feather boards, bowed workpieces used to cause me fits because they wouldn't lie flat. Narrow stock, which nearly always has some bow in it, was always the worst.
To cut consistent profiles on bowed stock, examine these workpieces and place them with the bow down where shown at top for best results. This takes the spring out of the board that occurs with the crown of the bow up. Use feather boards, but holding the workpiece firmly against the tabletop and fence at the router bit requires much less pressure with the crown facing down.
—from the WOOD® magazine shop