Hi John
Thanks for the reply. Being Christmas I didn't expect a response until January, so much appreciated.
Excellent, I've got a pair of 25w chassis mount 8R's for testing (you or Richard suggested these years back

) I'll use these to check for a flat trace.
I'm enjoying the winter OTX upgrade project & have stripped down the amp and drilled out the bolt fittings and grommet holes.
I've previoulsy applied the feedback lowering mod, so will swap the 2.2nF feedback caps C19/20 for 2.7nF for the Sowters.
I'll report back once the U082S's are fitted.
All the best, hope you're all keeping well and safe.
Jaz