Main issue with these plants is not their variability, which is not that big as is often believed.
It's the effect itself - with not so high dose you forget that you have taken anything and you get lost in dreamlike series of ilusions or events. If you are in safe environment, it could be ok, if not, you have a problem.
It is of course possible to ingest just proper dose, but it needs strong focus to find it (work with one batch of plant material, start very low, increase doses very slowly, never redose, no combinations with other drugs, well prepared environment).
Much more effort needs to be dedicated to this than with other plants. You could regret any fail in this area.
Ime and imo, the most important point is that it is not worth to do.
Mental effects of tropane alkaloids are quite similar to dreams.
If you ever had a dream which was confusing, produced some anxiety and fear, you already have very good idea about effect of tropanes.