Whatever floats your boat...
Just took a look at some Martin catalogs and noticed that like in 2003 with only the cable slide being used more bows are pictured with the cross above the slide then below. But no consistency. Looking at the 2011 catalog with the TRG on all the bows pictured, all of them have the cross below the TRG. I have heard it said before that it really doesn't matter, whatever works best for you.
I think on the single cam bows like mine, I prefer the cross to be above the slide as it creates a less acute angle of string to the cam located at the bottom limb and that the angle for the top does not effect lean because they are attached to just the outside of the axles. So for my single cam I am opting for crossing the string above the cable slide as I presently have it.
Dual cam bows might be better served by putting the cross below the cable slide thus creating a more equal stress on both cams and reducing cam lean.
Smarten Up and Martin Up