Actually, the score is not specifically meant to be read from left to right, top to bottom, or anything else along those lines (though it certainly could be, these are only a few of the many, many options).  I'll quote from the prefatory note to Folio (which includes Dec '52 and several other similar-ish works), which includes misc. extracts from Brown's sketchbook from late 1952 ...

"... to have elements exist in space ... space as an infinitude of directions from an infinitude of points in space ... to work (compositionally and in performance) to right, left, back, forward, up, down, and all points between ... the score [being] a picture of this space at one instant, which must always be considered as unreal and/or transitory ... a performer must set this all in motion (time), which is to say, realize that it is in motion and step into it ... either sit and let it move or move through it at all speeds."

"[coefficient of] intensity and duration [is] space forward and back."

"The composition may be performed in any direction from any point in the defined space for any length of time and may be performed from any of the four rotational positions in any sequence.  In a performance utilizing only three dimensions as active (vertical, horizontal, and time), the thickness of the event indicates the relative intensity and/or (where applicable instrumentally) clusters.  Where all four dimensions are active, the relative thickness and length of events are functions of their conceptual position on a plane perpendicular to the vertical and horizontal plane of the score. ... It is primarily intended that performances be made directly from this graphic 'implication' (one for each performer) and that no further preliminary defining of the events, other than an agreement as to total performance time, take place.  Further defining of the events is not prohibited however, provided that the imposed determinate-system is implicit in the score and in these notes."

There's also a cool little graph of a cube that I wish I could copy here, but the caption reads "space relative to conceptual mobility and transformation of events in arbitrary, unstable time."

Thanks for the welcome.  This forum is a real find.

How many performances did Augenmusik do?  Is the group still around?

You're from MD too, Evan?  I don't quite know what to think about you now.

Back to the topic, though:  I think Haubenstock-Ramati's graphic scores could benefit from the same "speculative mapping" that I mentioned with respect to December '52.  Maybe there are already performers doing this.  However, I believe (although my record when it comes to unverified assertions on the Radio 3 board is not stellar) that RHR generally included fairly specific instructions with his scores.  I wonder how closely performers tend to follow them?  Maybe they should read like Beethoven's metronome indications.