I do not think you would want to go to high. The wind across the roof traveling at 60 miles an hour wind could put a lot of updraft under the panel, couple that with a modest cross wind and that could cause a problem. You may want to put a wind deflector plate in front of it.
Mine is 2" above the roof and I used 8 "Z" mounting brackets on the panel. After 2 years and 10,000 miles it is doing GREAT..
2013 Jayco Eagle 284BHS,2012 Ford F150XLT, EcoBoost w/3.73, 250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller, Trojan T145 Batteries (260Ah), 1500 Watt Ramsond PSI, EnGenius WI-FI extender