I am having problems getting correct adjustments figure for a trapezoid. In
Excel 2003 it was in a range of 0 to 0.5 with 0.5 effectively giving a
triangle.

In Excel 2007 this figure now seems depend on the height and width as well
(ie if you have a short wide shape the figure to get half way accross is much
higher).

I have not been able to discern how this is calculated and need to do this
as I am creating a diagram with several of these used which need to be
adjusted as a ratio from top to bottom (which worked easily in XL2003)