Hey Johan, if it isn't too much to ask, do you mind taking a tape measure and measuring the height off the ground of the front tip of your Sports Design front apron?
Page 317 | 2017 718 Boxster Manual | Porsche iManuals
According to the manual link above the ground clearance of the 718 (measured at the lowest point in front of the front wheel arch I presume) is 112-113mm (assuming SPASM -20mm) up to 131-133mm (base suspension no PASM)
According to GregW in the thread linked above, his yellow 718 base Boxster with base suspension with regular front apron has the front tip of his regular front apron 7" (178mm) above the ground (he also noted that this point was 33 inches forward from where the front wheels touch the ground)
Since you have a Cayman S with SPASM and Sport Design Apron, that *should* make your front apron tip 148mm above the ground. (assuming -20mm drop from SPASM, and -10mm because of the front apron shape). If it is not... then we can calculate the exact value the sports apron changes things!
I don't know why I care so much, since my car is already built and I can't change the specs now... but I'm just very curious.