Booting intermediary Tails on MBP9,2 might requires editing boot menu commanddline
When trying to boot from intermediary Tails 2.10 installed using dd ocmmandline (from Linux though), the resulting Tails USB is recognized as bootable on a MBP 9,2, starts to boot but get stuck with a black screen and a top-left blinking cursor.
I can try to see if I can reproduce that bug using dd from OSX first,
and using another USB as well, and Tails3.0-beta1.
It could also be tested on different models of MBP as it might be hardware specific.