I've had my 15 four years this month. Closed those vents once, to see if I could tell a difference. Been open ever since. Sidewall discussion on tires is way overated, Have you looked at cars in the last few years? Sidewall or aspect ratio has been getting shorter forever and new cars ride just fine. One poster on this listing even said taller sidewalls handle better? Wonder why vehicles that are made to 'handle" have short sidewalls?
And the hill hold feature, Our new car has it. I LOVE it, stop, take your foot off the brake and vehicle sits there until you give it gas to drive off. Great deal. The other is soon coming to bikes, smart cruise control. Our car has that as well. I entered Smokey Mountains last friday morning and turned cruise on at 45mph. I never touched the brakes or gas pedal again until we got to Gatlinsburg. At times we were running 10 mph behind slow traffic, once almost stopped as car in front suddenly turned into turnoff, but we slowed, accelerated as needed, I like technology.