TDA8954TH Class D 420W Power Amplifier Board Tech Review and Issues is it worthy?

This amplifier is widely sold. At the specified 24V AC input it should be able to manage 300W per channel. I tried to get 420W out of one channel but got to 230W into 8 ohms on the left channel and it blew. Twice. We have a look to see if the build worthy of the now obsolete power amplifier chips? Dodgy board layout and inferior ancillary components might stop us...