[thstone]

It is not recommended to use a 5 or 6 pt harness with the stock seats. The problem is that the sides of the stock seats are curved which can allow the harnesses to slip down off of the drivers shoulder. Also, you'll need a seat that has a hole in the middle of the bottom of the seat for the sub belt to mount under the seat (which stock seats do not have and it is not recommended to simply route the sub belt around the front of a stock seat).

In order to use a 5 or 6 pt harness properly, a seat with holes in the back are typically required so the harness has a "straight run" from the mount through the seat and over the drivers shoulders. GT-3 seats work great and there are many aftermarket seats which will also meet these requirements.

In regards to mounting the harness, the stock Boxster roll hoops will work fine. You'll also have to add floor mounts to the sides and under the seat.

I use a Schroth harness in my race Boxster but there are many harnesses available and any good manufacturer will offer something that should work.