There is also a company out of San Rafael, CA that has been installing carbon fiber pop tops that are only 1" higher than the stock roof--so low you can't even tell that they are there and yet more stand up height than a stock van. Really great. A friend has one.
Currently converting 2016 170" 4x4 w/custom interior, electric system, hot water and air, and many other things. Past owner of 2007 Sprinter 2500 144" w/Sportsmobile Penthouse, Van Conversions interior and
solar, inverter, charger, house electrical by self.