the true skin is thin, waxy, indigestible and has zero alkaloids
the layer just under that, the green stuff has the highest concentration of alk in the plant, but data shows that in at least one species despite this layer having the highest concentration of alkaloids, it has only 1/3 of the total alkaloid of the plant
here is where i address this:
what is important to realize is that this layer is 1/10-1/20 of the plant in terms of mass, so having 1/3 of the total alkaloid is a big deal, if alk was distributed evenly this layer would have 1/10-1/20 the total alkaloid, but still the majority of the alkaloid in the plant is not found in this layer, rather the dry weight concentration of alk is richest in this layer
the waxy skin is a lot like that of peppers, of tomatoes and other things like that, it is indigestible, but not a source for concern and does not cause nausea, unlike mescaline.