It occured to me that Vanessa can do double duty. You can use Vanessa to find CG and to weigh the model.

All you need to add is a bathroom scale, a second pulley, and a suitable counterweight.

Add the second pulley at or near the same height as the first and far enough away from the first to be clear of the model.

Run the suspension rope through both pulleys, and secure it the same way as the original. Vanessa works as advertised in this configuration.

When you want to weigh the model, put the bathroom scale on the floor directly below the second pulley.

Fill a suitable container with whatever it takes to be heavier than the model. How much heavier is up to you, but an old gallon bail-type paint can (or two) filled with concrete works for me - some of my models exceed 35 pounds RTF.

Put the weight on the scale and attach the end of the suspension rope to the bail. Make sure Vanessa is suspended - what you want to find out is how much the whole schmear weighs - weight, ropes, Vanessa, and all.

Now sling the model in Vanessa and re-weigh the whole thing.

The difference between Vanessa empty and Vanessa loaded is the weight of the model.

Note that the loaded weight shown on the scale will be lower than the empty weight, because the weight of the model is trying to pick up the counterweight; that's why the counterweight needs to be heavier than the model.

( don't feel bad if you don't get that right off . . . I needed Excedrin before I got it down pat.)

If you have a scale which displays negative numbers (tare-capable scale), you don't even have to weigh the Vanessa rig empty. Just hook the thing up, get the model suspended, and zero the scale. Take the model out of Vanessa, and the scale shows a negative number equal to the weight of the model.

Even better, if you set up the weighing part while you're getting the CG chased down you can see directly how much weight you added or subtracted in the process.