Speaking of VFDs

I now have a VFD on Bridgett (Bridgeport Series II with Gecko G320s
installed). Question is, how fast can I turn the spindle safely. The
stock mill has a allows you to crank it up to 3500 rpm. The VFD I have
will do 180 hz so it could push the spindle up to something like 10500
rpm. Now I know that is way too fast and something would get destroyed,
but what would be a reasonable top speed to run for light cuts and small
end mills?

Tim
[Denver, CO]