I've rerigged a couple of masts - with solid wire shrouds - with a hole on each side, feed the wire in and up out of the top of the mast, then bend each to form around a bowsie and slide back into the mast. As mentioned earlier - sailsetc 'rigging guide' shows this method. It's really neat, but fiddly as hell to get the lengths right (and not get them wrapped round each other inside).
I favour one hole on the front face, with a single hook which the shrouds are crimped/wrapped onto. As Larry described. My current rig happens to have a heatshrink sleeve over it: a) stops it falling out while rigging (but so does a piece of tape...); b) reduces windage a bit (but then how perfect are your mark roundings and tacking...?)
I'm more bothered about getting equal lengths (i.e. rig upright port/starboard) than the ideal attachment method. Just keep it reliable, robust, and simple.