So I finally got the SV6s into my MTB build. Using Ackmaniac FW.
I started off in sensored BLDC and got the settings to a point I was happy with
Motor max: 80
Motor min: -70
Battery max: 45
Battery regen: -20
This worked well, good strong brakes and everything worked as it should.
Next I set up in sensored FOC with the exact same settings. Under heavy acceleration, on motor cogs so badly that it locks up the 8 inch wheel into a skid. Not what you want when you are braced for heavy acceleration 
Also, the brakes were super weak.
I bumped up the brake settings to -80 and -25. A little bit better, but nowhere near as powerful as they were on BLDC.
I have tried motor detection and a variety of different settings in sensored FOC and still have the problem of shit brakes and cogging under heavy acceleration (only on the slave side)
The slave ESC also has a problem where it won’t connect via USB on certain occasions. Its like it picks and chooses when it wants to connect. When it doesn’t connect, the computer tells me that the USB device has malfunctioned and can’t connect.
At this point I am considering just switching it back to BLDC and being done with it. But this board isn’t for me and I need to give it to the customer soon. I would love to be able to give it to him set up in FOC.
If anybody can suggest anything I might be doing wrong, it would be much appreciated.
@YUTW123 any ideas?