2x6 is plenty wide for the tires, and saves storage space, though it used in the driveway and left at home, it doesn't really matter. I used 12" 2x6s for many, many years. I had cut a 1" bevel on each end which reduced the slippage of the block a lot. I finally gave in to the light and tight storing, though ugly, Lynx blocks, but do look forward to trying my new Anderson levellers once I have a trailer again.
2017 Escape 5.0 TA (someday soon, I hope
2015 Ford F150 Lariat 3.5L EcoBoost
2009 Escape 19 (previous)
“Most folks are about as happy as they make up their minds to be.” — Abraham Lincoln