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If you must, Saris Bones is an excellent rack. They're made for 2 or 3 bikes. The Saris Super Bones is a premium model that should be safe for your car - or as safe as any bike rack can be that contacts the paint.
Just thought I'd post here in case someone was wondering how it works
Just fitted a Saris Bones 3 on my Boxster 987.1 (987.2 should be fairly similar) . I hooked the top straps to the trunk lid. You can also use the lip behind the roof but I wanted to be able to cruise to the race top down.
I hooked the bottom straps to the exhaust pipe. If you hook them on the inside of the tailpiece, the nylon doesn't touch the metal at all when tightened.
The side straps were tricky and are very important. I didn't want to use the fenders as they're soft plastic so I found a hole of sorts in the wheel wells. It's hard plastic, could even be metal. I then stuck duct tape on the body where the straps touch. Basically only on the sides for the side straps. I also wrapped the top straps with duct tape in case they contact the body. I also put 2 vinyl circles where the feet of the rack go to protect the paint but you can also wrap the feet in soft terry cloth. The bottom feet rest on the license plate. There's very little pressure there so no risk of bumper breaking.
I very happy with this as I've been looking for an inexpensive solution for years. And I can use the rack on my SO's Golf too.
I'd get one of the hitches that goes behind the plate and use a hitch mounted rack like the 1up, then you don't have to worry about damaing the trunk, plus it holds the bike by the wheels not the top tube, less movement of the bike, and it'll hold a mountain bike.