I put some Swift springs on my new-to-me 2015 F-sport today and tried to put some 20mm wheel spacers in the back to get the wheels a little closer to flush.
I used Ichiban V2 spacers, which bolt to the hub and then the wheels bolt to them. The stock studs stick too far through and won't let the wheel seat flat. I've seen on here people running the 20mm in the back. Am I the only one with this issue or did everyone swap out the lug bolts?

 

Most people change out the the stock studs, depending on the spacer and wheel setup. The stock lexus wheels actually have little pockets in the back to allow the studs to sit in. You shouldnt have to change the studs with 20mm spacers and stock stubs and stock wheels.