Good advice posted above. Since you reload, try heavier 158 grain bullets, that may help your elevation issue, and possibly help with the windage as well. Another option r/e the windage issue is to file the rear sight blade a little wider on the right side if you continue to shoot left. It will bring your groups right, and if you mess it up, rear sight blades are cheap and easy to replace. If you are dead set on installing a red dot, I think B-Square used to make a no gunsmithing mount for the Security Six at one time, though I doubt they still do, do to the time this gun has been out of production. A good gunsmith could drill and tap the top strap for not to much $. A good red dot sight can do wonders for shooters who's eyesight is not what it used to be..
Larry