No I don’t have a Boxster but a mate has a 59 redg S’ and he uses a Saris Bones 2 but only one bike on it. The lower straps go underneath the rear valance and the top two go in the grove behind the hood (there’s a seal there and he just pushes the metal clamps in) he’s got some soft cloth duct taped to the lower straps where it touches the bumper/boot so it doesn’t scratch and uses the side clamps either side of the boot lid. Ive only ever seen the car parked but even with the rear spoiler “up” there’s enough room as he’s set the rack up quite high. It does foul the number plate but he’s not bothered about that.
That any use?
Can you not try one for a Saris Bones dealer ?
Or in his case he bought it from Evans Cycles who offer a full refund policy if it doesn’t fit etc..
Edit.. He takes the wheels off and sticks them in the passenger seat too, so it’s just the frame on the rack.