Steve Dawson designed the Class 5 amp...he's not a hack and he's certainly not a villain. Here are his quotes regarding the Class 5:
"Nothing has changed from the old circuit to the new one except the 'bedroom trick' is now integrated on the output. The old version or the new version is not bothered by impedance mismatch of 4, 8 or 16 ohms. It is optimally designed to deliver 5W into 16 ohms but will give less into 8 and 4 ohms."
"The output transformer is designed to give maximum power transfer of 5W into a 16 ohm load on the combo. If the load is reduced to 8 or even 4 ohms then maximum power transfer will not be attained. However the difference in perceived volume may be quite minimal in relative terms."
Would I connect my Super Lead at 16 Ohms to a 4 Ohm cabinet? No. Would I worry about connecting a Class 5 head to a 4 Ohm cabinet based on the designer/builder's advice that the transformer is designed to handle that? No.
Read the thread for yourselves. http://marshallvintagemodern.com/viewto … 851#p68851