Package Shelf Versus Standard Cage Kit - What is the advantage to the package shelf version?
The package shelf version of the cage kit gives you the ability to move the seat about 3/4” more rearward than the standard cage kit due to the placement of the main hoop.
On the standard cage kit, the main hoop goes all the way to the floor of the car and lives on a 9 degree angle. With the package shelf version of the cage kit, the main hoop does not go to the floor and lands up on top of the package shelf. Since it lands on the package shelf the hoop is installed straight up and down at 0 degrees.
When installing a seat in these cars if you place the seat as far rearward as possible the Left shoulder wing on the seat can hit the main hoop depending on the type of seat you have. If you have the package shelf version, then the main hoop is no longer in play for the shoulder wing on the seat to come in contact with it.
Many other people do package shelf versions of a cage kit but they put S bends in the door bars at both the front and the back of that door bars.
By putting the S bend in the door bar you have effectively weakened the tube at the point closest to the driver, which we do not feel is a safe way to build those door bars. Bending a tube is weakening a tube and where the door bars live and the function they perform we feel that it is a significant compromise to driver safety when it just isn’t necessary.
So the biggest benefit of the package shelf version over the standard version is to get just a little bit more room for moving the seat all the way rearward. Some people go to this option simply for potential re-sale of the car later to a larger audience of people.