I have been told that you start moving the CG back until the plane becomes unstable during High Speed.   Me I am from the school of carrier and fly what looks realistic to me.   Maybe Billy B. will chime in on this.   I know I can get a Bi-Slob to hang.   Really I just need to get out and fly more often.   

Doc, you called it! Here's my $.02.

If you're not sure how to get into a hang, try this. As the airplane passes directly downwind (wind at your back), chop the throttle and crank in a bunch of UP to try to hold altitude. If you can get the nose up about 30 degrees or more without climbing, add a bit of power to help maintain altitude. Directly downwind is the best place to try this because this is where the airplane will naturally want to sink, and also the wind will help keep the airplane out on the end of the lines. If you can get the nose up for a but but not sustain it, add more tail weight. You can wrap solder around the tail skid or the aft fuselage as you experiment, then install permanent weight once you are satisfied.

The things that indicate too much tail weight are the inability to maintain stable high speed, or the airplane wanting to go excessively nose up or over backwards in the hang. If the high speed is unstable but you still can't maintain a good hang, you may need to reduce your elevator movement, or adjust a bit of down into the elevator. If the airplane seems like it will hang but won't stay out on the lines, you need to add tip weight, engine offset, or move the line guide back if you don't have a slider. It's a balancing act (literally!), but once you get it, it's almost automatic.

Good luck, and keep asking questions.

Thanks to both Bill and Eric for the info this old man keeps forgetting.

Thanks for the great advice.  The plan is to put me and my airplane to the test this weekend at the Skyraiders contest in Auburn WA
Thanks
Darrel