>You can solder the 2-row headers top side.
> That sounds pretty good; fast and easy.
>
> I am laying out some two-sided boards, at the moment. I would like to use
> 2x20 pin headers, with some surplus (new) IDE cables that I got (200
> of them, new, for $5!), to make board-to-board connections.
>
> One problem is that the headers sit flat on the board. So in order to
> connect them to both sides, it seems like I'll have to put another row
> of holes next to each side, and solder on both sides of those holes.
Just keep 2mm distance between the board and the molded plastic and hold
the iron relatively flat against the board when soldering.
Done it, worked without a bad connection (~100pins).
You could get longer headers if you like (e.g. wire-wrap version) but it
works
with the standard ones too.
ST