I asked RB about this, but I'll ask here too, as I'm interested in other viewpoints.

I've heard this can be done, though I suspect it's very rare (or maybe it's just very rarely talked about). There's an example of this in the book, Magus of Strovolos, IIRC.

What do you think is involved for an astral projector to appear in the flesh temporarily in the physical world? Or even just becoming visible to a person?