I'm going to try one with a small bit in the mill. GM got it from nasa
https://www.nasa.gov/topics/nasalife/friction_stir.html
My "donor" ebay e92 seemed dead dead dead, tunercat couldn't see it, scanner couldn't see it then as a last ditch efilive saw it was an e92. Woah, so then I tried to read it in efi and it read, very mysterious, it acted like it read a pretty big chunk in just a few seconds, then continued on like normal. Of course the file was junk, only saw the OS. It gave me a bit of hope so I used the recover function in tunercat and about an hour and a half later it finished, no vin, no seed, no traceability etc. So, I wrote it again(with a 2014 file I had just read out of another e92) and now it programmed in about 20 minutes and populated modules 1-6. Did it again and this time it wrote the vin and traceability came back although a different number than the donor 2014 file. So, I guess what I am saying is it's breathing a little life now but still a good donor
I'm not sure I will have time to mill the back plate off this weekend but I'll try, paying jobs come first since who knows in the current climate when that will dry up.
I would like to talk more about the "slave" chip you did. If this isn't a good place, we can pm or I can start another thread. The small 9mm x 11mm BGA chips look to have never been made so I will order some 11mm x 13mm bga's next week then have a few boards made for pogo sticks as money allows. NSFW's 3d printed jig for the Blue/red and Blue/green PCM's is super cool and would be nice to do that for the e38, e67 and e92 too if we can figure out the bdm stuff for it.