I've got them in mine
The rear eyelets use the rear seatbelt mounts, one of the fronts also goes in the seatbelt mount and the last one fixes to the trans tunnel with a FIA plate
The rears should be higher really, but without a cage you stock tbh. I did look for a harness bar, but couldn't find one for the S15. Mazworx do one for the S13/14, but when I measured the width of the car they were not the same