This is a big forum so chanses to find someone here with that combo are good.
In the meantime I can reply with a slight variant answer.
For years I'm used to the 300F4 and I found it to be one of my best lenses so I use it alot.
Since the 150-600 came out I was the first to acquire one in my hometown.
I use the Tammy with a 600D, a 5DII and 5DIII and until now only with the 5DIII there were some AF mishaps at AI-Servo.
I'm blown away by the IQ (mostly wideopen) in that matter that I'm actually considdering in selling the 300F4.
Too bad for the loss of 1,5 stop but for me Tamron succeeded in making a 600mm handholdable and affordable with a quality certainly not to be ashamed of.
I sold my 300 F4L IS as well - haven't missed it once. The Tamron VC is really impressive.
I still have the 400 5.6L but its just been sitting on my desk since I picked up the 150-600