Thanks for your response.
I made the suggested change from 2 monitors to 1 and now have it
working as desired but only when moving the mouse from the slave
screens back to the master: moving the mouse to the bottom of the
right slave monitor transitions over to the corresponding position
(appropriately scaled) along the upper right-half edge of the master,
and similarly for the left slave monitor. But when moving the mouse
from the master to the slave, the entire top of the master appears
connected to the entire bottom edge of just the primary screen on the
slave (monitor with the toolbar).
In the nView tool from Nvidia to manage the desktop I found an option
to extend the toolbar across both monitors so I tried this to see if
configuring the desktop in this way would convince ID to use both
screens when transitioning from the master to the slave, but still no
luck.
Is there something else I should try or is this something you might
try to rework in a future release?