Quartus/Timequest and extended temperature

For Cyclone III (EP3C10F256), Quartus does not show any industrial-temp versions as "available devices". The Tech Bulletin extended temperature support for cyclone ii, cyclone iii, and max ii devices states:

"For extended temperature operation for Cyclone III devices, Altera supports the use of industrial-grade devices with de-rating. Customers wishing to use Cyclone III devices over the extended temperature range must compile their designs in Quartus using the -8 timing model."

Derating to a slower commerical model doesn't seem to clearly address operation at -40C, because the devices tend to be faster at lower termperatures. At the same time, you want the tools to account for the faster as well as slower variations in the timing model in order to generate a fit & route that works across the entire range.

So the question is, is this really the correct way to compile a Cyclone III design for use over the industrial temperature range, with some assurance that the result will work consistently on production boards?