Cup holder Mounting Question
 

Hi,
I need some help. I bought a seat mounted cup holder & mounting screws. I am trying to figure out the proper way to attach the screws to my 94 XL F150 bench seat. (This cup holder - http://cgi.ebay.com/ebaymotors/92-96...2em118Q2el1247 )
I am not sure exactly where the screws go in. I felt the front of the benchseat from the bottom up and there seems to be a metal rail that goes up about an inch, then it feels like there is a second metal bar.

Does anyone know how to attach the seat mounted cup holder to the bench seat? Should I drill into the bottom or top rail? Am I suppose to drill a pilot hole then use the mounting screws to do the rest? (They look like self tapping screws.) About how high should the holes be from the bottom of the seat? If you have any pictures feel free to send them along.

Thanks you very much I really appreciate the help!!,
Tom