Check the list of the finished projects
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/25705772/srt/pa/pging/1/page/1.cfmThere is at least one installation with the height equivalent to MORE than 4" bracket, by Bigfootford:
http://forums.woodalls.com/Index.cfm/fuseaction/thread/tid/24783458/srt/pa/pging/1/page/2.cfmHe made 3x3 bracket, and attached the leg with the top screw in the leg (i.e. in the panel frame) that appears to be at least 1" higher than the bracket. So this is at least 4" from roof to panel screw. None that his roof is NOT a plywood with rubber, but a fiberglass, though not as thick as on boats. Not sure, but 90% positive that he used "well nuts", not tapping screws, so ther is no issue with screws pulling out of the roof.
