Speedometer will of course read slower than you are really going. Nor is that how I would proceed. Keeping in mind rim Rash, I would be tempted to increase tread width, knowing I got an increase in tire height along with it. The stock tire is 28" tall and prone to rim rash. What you suggest is 29 inches tall, will be off by 3.5%, and does notihing at all to protect the rims.
A 275/45R19 is 28.7" tall so taller, but not quite as much, adds 10mm of rim protection to the outside (enough), and adds considerable air. In fact, it would probably ride better. One thing most don't realize is the intent of the tesla tire size it to place the sidewall very uprights. That restricts movement up and own and thus increases range. At the expense of ride, for the sidewall has a hard time flexing. Getting a wider footprint helps the ride too as the sidewall can now give more easily (the "bulge" is farther outside the rim width).
Of course the speedo will still be off, but not as bad. It might not be a fantastic snow tire that wide, but as a 3 season tire this would (assuming no interference), be a hands down better decision.
One mans opinions of course, but then I'm already tire shopping for mine too. Above is my present thinking.
YMMV.