As the guys mentioned already the Vanessa won't tell you where the CG NEEDS to be. It's just a replacement for your fingertips to show where it's balanced at the moment. It doesn't replace the initial calculations you do with the online CG calculators.

It's also not really any better than your finger tips or using sticks with soft rubber pads on smaller and simpler models. What it does best is hold up larger bulky models well so you can work around them and adjust the CG by adding or removing weight or shifting parts while the model is held suspended. Another good time for a Venessa rig on even more compact models (like under 5ft or 1.5m span) would be if they are biplanes or have troublesome wing struts as on some scale models. But of course if you go to the trouble to make one or two different size rigs to cover the whole range of sizes then you might as well use it. The other "of course" issue is that you need to hang the model in the rig from a ceiling hook. Not everyone is in a situation where they can easily drill and screw a hook into the ceiling, Renters or finished ceilings and such. For those cases perhaps a set of double doors can be opened and a bar set across the tops of the doors or some other open area with ledges can be used?

In the end though for smaller size simple models it's hard to beat just using our fingertips. There's no setup time and they don't take up any room...