agree w/ Stein, 6', or more even, between loops on the main line.
what i do with my long line setups is actually both, it's a texas rig, full line length, w/ a gang line clip. Keel grabber weight with a bungee, just like a normal block setup, but run the tail through the keel and then attach your gang line clip, pull off whatever you want your drop to be (~2' for me, but you can always change it this way) and hold the clip and that slack in one hand w/ the decoy and wind the rest around the keel with the other, then just wrap the drop and clip back around the keel. It does NOT save weight and if you use the bigger clips they'll rattle around in the bag, but the same decoy can be used on your long lines or for tossing, and the line clip can be used as a depth adjuster when throwing them as singles. I keep most of my diver blocks setup this way; somedays the big river requires a full raft, others i'm mixing in a handful in some pocket with coots and widgeon