Thanks for the help, Pragmaticskier.
I tried your suggestions, but I cannot remove the racks from the center locking mechanism. The only solution I can see, is to remove everything including the center locking mechanism and the two sliding brackets from the ski, then drill out the rivet connecting the rack to the mounting plate and drill a hole in the rack in the desired position and rivet it back to the rack.
That's getting too complicated for me. I guess I'll just sell the skis. Does anyone else have any suggestions?