The DX8 I'm using with this 850 has five proportional chs, two 3pos switches & one 2pos switch. So that leaves one proportional (dial) & one 3pos to try to operate this Sabertooth.
I have the turning on the 3pos & all I could get it to do was either off, turn right slowly or turn right quickly. Couldn't get it to turn left.
So I started monkeying with the mix, making aux3 (dial, for/rev) master & aux1 (3pos, turning) slave. Master has a bit more epa than slave, also factored in negative offset & F Mode 2 to turn mix on (0 or 1 is off) and now it works left/right!

But only if I'm moving for/rev.
I just watched your DX10 vid PFB, I hope my thumbs are long enough to reach the sticks!

I think the DX10 will be the ultimate for any constr rc.