Hans:  You don't absolutely have to use the Porsche kid's seat, but you do
need the "kit" that installs under the front edge of the seat rails and has
a latch on it.  Generally, this must be installed by a dealer who has to
plug in a connection to the seat belt system and then they have to enable
the latch on the car's computer...using their own diagnostic computer.

You do need access to a Porsche child seat to trace the size and shape of
the tongue on the belt that comes off the front underside of the child's
seat.  Normally...you would shove this tongue into the latch just under your
car's passenger seat; however, if you trace it....which is what I did, you
can then cut a piece of metal or lexan (plastic) that when slid into the
latch will make your car's computer think that the child seat is there...and
it will shut off the airbag.  When the air bag is turned off, the warning
indicator under the instrument cluster will flash on and off for about a
minute to "warn" you that the airbag on the passenger side is disabled.

Hope this makes sense to you, let me know if I can provide any additional
information.

Regards from Texas...