My existing fuel cap on my '99 C2 doesn't have a tether strap so I purchased a replacement porsche item with a tether thinking it would be a straight swap. I've come to fit the new cap and there is no obvious point to fix the tether strap to (I bought the little plastic rivet too). I've tried the hole behind the hinge spring but the fuel flap won't close fully. Is my car just not meant to have a cap with tether?