Hi DB, a couple of questions/thoughts.
If I bought an SO8-Dip-8 adapter without stand-off type leads (something like the one below), attached the op-amp, and then laid it directly on the pcb I would be able to just solder some short leads directly through the board/pcb. Would this get me to where you are suggesting going with this? (this is pre-supposing of course that there is room and nothing under the position that can short)
View attachment 1303862
In "decoupling" do I understand correctly that you are meaning a small (0.1µF?) cap from the supply lines to ground?
Can you show us a photo or 2 of how you added the 1612 to your amp(s)?
Also, one thing that I've never seen in any Yamaha amp etc is a part that wasn't of Japanese origin. And the OPA's are from Texas Instruments. I think that we can wait a long time before they use an op-amp that wasn't sourced from Japan.
Cheers,
James