> [Surprisingly large .cmo / .o files]

It's hard to say what's happening without seeing the source or the
generated assembly code.  If that kind of things doesn't scare you,
just compile with ocamlopt -S and look at the resulting .s file.
However, I'll venture a guess:

> Obviously, there are a lot of fields in the record type, and I
> assume that this is where the blowup is happening, but I'm not at
> all sure where.

OCaml 2.01 had a known code size problem with the
{ record with lbl = newval } construct, when "record" belongs to a
type with many labels.  This was fixed in OCaml 2.02, however.

Regards,

- Xavier Leroy