From the left turn lane I can make a U-turn directly into the #1 lane. That's certainly nothing to complain about! I, too have slightly wider tires than stock, and they rub just a tiny bit when at full lock. Nothing you can hear or feel, but there's a shiny spot where they have been rubbing on the suspension.

Rather than adding an adjustable stop, I'd look into some spacers. Mayby as little as 1/2"?