Since it is a Winegard, there should be a mount made by them for it. Other than that, put it in a place where you can most easily run the coax thru the roof to the receiver. Be sure and use plenty of Dicor self-leveling sealer on any screws into the roof and where the coax goes thru it.
Thinking ahead--do you always expect to be able to park where the sat will have an open view to the southern sky?
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired