A 10mm studless spacer
will not 1) give you enough thread stud engagement to torque down the lug nuts to factory 20in wheels and 2) give you enough hub depth for the wheel center bore to seat too. A 8mm studless spacer (for factory wheel) would be the limit per Ian Pavelko (Director of Technical Services) at Fastco Wheels per this video below. It's highly informative especially at 3:00, 10:40, and 14:45 (where he mentions the 8mm spacer) sections of the video. Also useful is his post (and proceeding post) regarding Model 3, Model 3 Performance, and Model 3 Performance w/PUO wheels here:
Aftermarket Tesla Model 3 Wheels and Tires - Tesla Owners Online
As a FYI, this video was made in 10/2018 and since then Ian has confirmed the hex bolt is only on there to help hold the rotor in during factory installation. It's not needed afterwards.