We are attempting to re-create this wonderful
light French pastry, but although our batter
does form a nice skin, it then falls and cracks
before the baking is finished. We have varied
the amount of folding and temperature in the
oven to no avail. Any suggestions?

Well, no answers to the question here, but after
10 tries with 2 recipes, we are now making
1 1/4 inch diameter macarons which closely
replicate those we have had in chocolate and
pastry shops in Paris. The problems were in the
amount and way the batter was mixed as well as
how to deal with an oven that usually is in a
bad mood.

...an oven that usually is in a bad mood...

I understand completely, mine has decided to have a major case of PMS. Top of rack is raw, bottom of rack is burnt. Go figure. And the temp won't hold, one minute too hot, next minute too cold. Some mornings you just want to kick it.( very painful, I do not recommend it)