First, see how it works with the smaller pan.
Then, use an oven thermometer, calculate how far off the oven temp actually is.
You may be able to just make a simple change in the way you bake to compensate for the variance.
Lots of stoves can be adjusted to the right temperatures by a technician with no need to change the thermostat. In fact, some stoves have a means for the owner to make adjustments themselves.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan