[graphviz-interest] Big graph, not following rules?

I am (still) making family tree graphs (thread: forcing distinct/more ranks?)

With just over 700 people in my tree, it's pretty
big, to the extent that looking at the whole thing
is increasingly meaningless.

However, I have noticed that in local areas my "rules"
are being ignored.

My rules are (roughly).

* Children are draw below the marriage that produced them.
* births have an associated date
* marriages have an associated date
* the set of all dates (derived from the above) is placed
   in an invisible sorted list, with all events on that date
   given a "rank=same".

The overall intent is a drawing where
the vertical position on the graph is monotonic
with date, and the rest of the tree follows
ones normal expectations.

However, as the tree has got larger and more crowded I see
more and more regions where these rules are broken.
The most obvious breach is of "rank=same".
On checking, I have found a few cases where marriages
are subsequent to the birth of children (ahem),
and my code (as first written) didn't take account of second
marriages.  However, a very large proportion of the data is "quite plain".

Is Graphviz breaking my rules in order to follow more general
placement contraints? Can I give Graphviz more "slack"
on these general constraints in order that my rules are
more closely followed?

I don't mind a lot of slack white space on the drawing
if local areas can be made better because of it.

If an example is needed, it will take a while,
since I'll need to anonomise the (personal, private) data.

  BugBear
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