GraphViz dot Circular Node Alignment

How to use Graphviz to align nodes circular in clusters with additional text? Optionally with identical node positions (always 8 nodes per cluster)?

I tried circo, however, faced some shortcomings:

• No clustering
• No comments
• Problems with margins for larger labels (10+ char)
• Alignment varies with label size

This (Graphviz Online), nothing spectacular, was the closest I could get. Any hints to other layouts (or even tools) appreciated.

graph {

layout = circo;

node [shape = circle,
      fontname = Helvetica,
      margin = 0]

edge [style=invis]

subgraph 1 {
a1 -- b1 -- c1 -- d1 -- e1 -- f1 -- g1 -- h1 -- a1
}

subgraph 2 {
a -- b -- c -- d -- e -- f -- g -- h -- a
}
}

Not exactly the answer as I was asking for (Graphviz), but I found a much nicer solution with MATLAB. It was about plotting a seating plan for an event.

What I did broken down:

• imread() image of the floor plan
• Roughly determined pixel spacing, used as x & y vector for image() so that tables are in scale with the room.
• Manually defined centers for the clusters (here tables) with the help of ginput() (or imellipse())
• Plotted circles with plot() and added text with text()