I'm posting my reply here as well as at the other occurence of this topic.
The expert advice I solicited suggests that the numerator and denominator be runover in the spatial fraction and a tn inserted to explain that all of the results of the cancellations are "1".
So the numerator and denominator would each be divided at a multiplication dot and centered over the horizontal number lne. Don't put in the 1 above each cancellation but deal with that in the tn.
Hope this works for you.