Setting the constraint "NET <netname> FAST; " in the UCF file for an XPLA3 Webpack
project has no effect on the slew rate of the output.
Change the default Output Slew Rate option to "FAST" in the Implement Design -> Properties menu.
If you need any outputs with slow slew rate, add the "NET <netname> SLOW;" constriant to the
This will be fixed in WebPACK 3.3.