99% of commercial mobile radios were designed around end users who made short transmissions in bursts - dispatchers, drivers, etc... They were never intended for the 50-75% duty cycle that the hobbyist/gmrs world utilizes them for without additional cooling. Hence why they run extremely hot if you are BSing for 20minutes or longer. The UHF CDM is intended to be run at 40watts in high power. Additional cooling such as a small fan on the heat sink would be a good idea depending on your talking habits. The reason the software allows you to program up to "48watts" is to adjust to 40watts without having to do an alignment/power calibration on the unit in the field. Depending on soft-pot settings sometimes "42" gives you 40 or "46" gives you 40 etc... -RfMedic