I use ABG mix, so I'm not sure that this would be a proper additive for it, but I'm very interested in Brent/Matt's view on the soil world.
If you're thinking of the clay in terms of using it as an additive in more organic substrates, I think you're missing the philosophy behind it (I'm not picking on you at all, Scott--just pointing out the idea of using it as an additive, which has popped up in nearly every thread about soil). Organic substrates are useful for growing plants. A clay-based substrate is about helping bridge the gaps in the ecological cycle in our vivs and the overall health and well-being of the frogs contained in them.
Organic substrates break down into muck and lose their structure over time. Clay-based aggregates hold their structure, providing a permanent habitat for microfauna to inhabit and repopulate. Adding aggregate to an organic substrate defeats the purpose, because you eventually end up with clay particles surrounded by dense muck--there isn't any suitable space provided for inverts.
Dealing with clay-based soil is a complete shift in mindset from working with organic substrates. I don't see that the two can be cohesively integrated.