A request from a non member

[pwdrive]

The 20 watt resistor is rated at just that ie: 20 watts max dissipation without any heatsink, with the unit all up and running and hunky dory measure the voltage either side of the 20 watt resistor, from that you can determine how many watts it's dissipating with the unit functioning normally, post the voltages measured either side of that resistor on the forum.
The two voltage readings should not change over time, if the output voltage from the resistor changes over time then you need to investigate.

Lawrence.