Does not seem to add baking time, but keep checking, as the temps are not that accurate in those ovens. Just put the baking pan on top of the stone. My stone did crack, but still works fine to help distribute the heat more evenly!
Tina & Ted & pooches
2012 Ford F-150 XLT 5.0L V8 4x4 with tow package
Andersen WD hitch with sway prevention
2012 Rockwood UltraLite 2304s trailer