Adding 4th Axis to LinuxCNC with 7i92/7i77/7i76, Use absolute encoder or incr?

So I'm adding a Tsudokama RZ-160 rotary as a full 4th axis.   I'm replacing the existing TPC-JR with a standalone drive and wiring everything direct.  I have a good handle on most of this, however I'm left with the choice in the title.  The encoder is an absolute encoder wired directly to the drive.  The drive then either passes along the serial absolute position OR has outputs for a simulated incremental encoder.  I know how to wire the incremental, it's the same as my other 3 axes, and can get wired directly into "Axis 3" on the 7i77 board.  However, the RZ-160 of course does not have homing switches (that I'm aware of), so repeating the same location with the incremental encoder output through a power cycle may prove challenging.  At the very least, I'd have to break out an indicator and indicate in the 4th if I understand correctly.  With the Absolute encoder, in theory, I'll always know where the rotary table is at.  I don't know that that is accurate, and it may only remember location within 1 rotation of the motor, which is 1/60th a rotation of the table.  Is that accurate?  Can the PSO /PSO output be wired into the 7i77 SSerial port easily?  Is it worth it?How would you set up your 4th axis given this choice?  My drive is a Sigma II Yaskawa drive (SGDM-04ADA, same as what is in the TPC-JR), the servo is a Sigma II (SGMPH-04A1A-TF11).

Thank you

I think I'm seeing the lag while attempting to tune the axis - ferror is oscillating between over and undershoot the whole time very fast. Not enough to feel it, but enough to hear it. I've been reducing P to try to compensate for it, but that's been pretty futile. I think the drive is lagging, so linuxcnc tells it to speed up, then it reports overshoot, linuxcnc tells it to slow way down, rinse and repeat. That or I have an encoder/servo problem, and I don't want to replace that ($$). I may try getting the servo info direct, but I'm not sure how.

How is the drive connected to LinuxCNC?

Analog output on joint 3, feedback like a normal encoder, but is from the drive which is taking in absolute encoder data from the motor - this isn't an ethercat setup or anything like that. I was also getting encoder communication errors at the drive, so I'm going to try another encoder.

EDIT:  Connected to a 7i77, which is connected to a 7i92.