Barbara since you mentioned floats spanning some or all the columns
does AMS have any rules about the relative _order_ of these float areas.
latex always keeps floats in order. It's fairly clear that top of page
is before bottom of page, but in general it isn't so claer what `order'
means. If you have a single column float followed (in the document
callout/reference order) by a double column float can you typeset
them as

--------------float 2 -----------

----float 1 --

or do you have to have

----float 1 --

and defer

--------------float 2 -----------

to next page.

If you allow the former would you also have allowed

--------------float 1 -----------
----float 2 --

ie consider just a partial order on float areas with either
the single or double column top being first.

if so would you allow

--------------float 2 -----------
----float 1 --
----float 3 --

and similar permutations on a theme.

the algorithm is really quite a bit simpler if you can impose a strict
ordering on areas (it doesn't matter what the ordering is) but that
might be too rigid. But once you open up the possibilities of partial
orderings on the areas, there is a danger of combinatorial explosion in
the number of possible arrangements that need to be tried.