you need the anti-sub belt attachment that goes under the front of the seat made by Brey Krause or Porsche.
http://www.bkauto.com/porsche/r9030.php
http://forums.rennlist.com/rennforums/showthread.php?t=161496&highlight=belt+attachment+GT3
these instructions are from the Racer's Group(707.935.3999) :
For this install, you'll need:
-Schroth Harnesses, snap in lap and snap in sub belt style.
-BKR9003 (1 set, 2 pcs per set)
-BKR9004 (1 set, 2pcs per set)
-Porsche Genuine or BK sub strap attachment bar. Both bolt up to the existing Euro GT3 seat brackets. The TQ sub strap bar is about 1/2 price of the BK bar; however, the TQ bar does not have any attachment for fire extinguisher bracket the way the BK bar does.
-2" opening size D rings, for sub belts (you'll be removing the snap feature from the sub straps and wrapping them using the D-rings.
Install the BKR9003 and 9004 onto your seat brackets, the outside one can also be attached at the roll bar/3pt seat belt attachment point on B pillar.
Remove the snap style fasteners from the sub belt straps. Wrap the sub belt straps around the sub belt bar and secure by looping through the D rings (same method as attaching the shoulder belts to the roll bar). Attach the sub bar to the GT3 seat brackets (after removing seat from brackets). Tighten them up at the D rings for minimal slack, the sub bars on these cars are close to the camlock and you'll have a lot of slack to deal with.
p.s.
I still have not done this! and my GT3 front bumper is also still siting in my garage!
