I run the weight off of the short side and my leader off of the longside. That way, my main line and leader are inline with the dropper coming off at a 90 degree angle.
The spreaders I use only have swivels on the long side axis. The short leg has a snap.
might depend upon whether you intend to fish right at the bottom, or if you just want to "get down there."
the spreaders we use for walleye are called "bottom bouncers" and typically have the weight BUILT IN to the long side, about half way down the long wire. the idea is to avoid snagging while you tick the end of the long wire on the bottom, with the lure and bait thus up from the bottom only a short ways. all of this is based on the theory that walleye dwell and feed very close to the bottom.
i used to use spreaders home-made from a coat hanger for hauling a herring down 120 to 140 feet to catch canary and rasphead rock fish. both wires of those spreaders were about equal.