where is the chakra system located?

[Plenum]

To each vibratory spectrum there is 1 body. In 3D this is the yellow-ray body. Yet there are 7 sub-bodies of the 3rd density body; meaning: although the 3rd density's physical complex here is human, there are "levels" to this archetypical body—that is, some human bodies are closer to 2D's vibrations, whilst others are closer to 4D (or in other words, one 3D body could be categorically "measured" as being a 3.1 body, another 3.4, and yet another as 3.7, if that makes any sense).

Same applies to the other densities.

Is this what you were referring to?

yes, that was what I was referring to. The 7 sub-bodies, which we may label as 3.1, 3.2, 3.3 ... ... 3.7.

this is DISTINCT from the phenomena of dual-activated bodies; which is the phenomena of 3rd density graduates from other star systems incarnating here early, to do 4d work in a late 3d environment. They have both 3d AND 4d bodies activated; it is regarded as a privilege, apparently to have such an opportunity.

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Ra mentions specifically that these 'other' 3d bodies can be explored whilst in this density.

The light body or blue-ray body may be called the devachanic body. There are many other names for this body especially in your so-called Indian Sutras or writings, for there are those among these peoples which have explored these regions and understand the various types of devachanic bodies. There are many, many types of bodies in each density, much like your own.

I am still at a loss at to why the Indians/Hindus were privy to this knowledge. All our terminology regarding energy structures comes from their literature (primarily as an infusion from Ms Blavatsky and her Secret Doctrine book).

who were they in contact with?

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Don clarifies, and is acknowledged for his summary, here:

http://www.lawofone.info/results.php?s=51&v=e&ss=1#5