Yes. License keys are stacked on an EEPROM based on their $$ value, not the number of outputs they cover. Stacking two 2-output $5 keys is the same as adding a single 8-output $10 key. If you stack a $5 key with a $10 key it will enable 16 outputs (the same as a 16-output $15 key). Stacking another 16-output $15 key would cover 48 outputs total on that cape since it would be the same as purchasing a 48-output $30 license key.