I'm not a lawyer, so this is my opinion, and nothing more. There are non-penetrating roof mounts for antennas and sat. dishes, available in lots of places, like this one:
http://www.solidsignal.com/pview.asp...-%28frm-166%29 Some are centered, and some are offset, and they come in different sizes. If it were me, I'd use one of them, and stick the antenna over the rail a bit (or not), like the dishes are, but since it's just sitting there, you can always pull it back. With the offset style, and the already asymmetric ANT751r, you can mount it on an offset mount and hang it over the rail, or spin it the other way so the mount is under the antenna and it doesn't go past the rail. Decorate with some big patio pavers (16" square maybe?), and some potted plants, and it doesn't have to look terrible.