What determines the size of a shape when you export a diagram as a shape?

[Chris G <cl isbd net>]

I'm trying to create a very simple shape comprising two lines linked by
a short arc.  The trouble is that when I export to a .shape file the
resulting shape is *much* too big, much bigger than its size on the
diagram that I exported it from.

Is there any way to control the size?

-- 
Chris Green