Well the 968 spare is a 16" and the Boxster spare is a 17", that being, the jack holder actually fits in our spare, it sticks out a little bit but it actually kinda fits even though it sticks out a little bit
BUT
how it fits, it is totally in the way of the bracket that sits under our spare where the screw goes in. I might be able to cut away form the foam to make it fit, but i think the bracket is way to large, and just putting the Boxster jack in a pouch would do much better and just lay it under the spare in our trunk, or in one of the sidewells.
On a side note, i deflated my spare after i used it byt removing the schrader valve and letting the air out, it went back to its mostly deflated state, i would say about 92%. It fit close enough to get it back in the car, but later i removed the schrader valve again and used a ratchet strap to get the rest of the air out and i would say its 98% deflated, which fits alot better.