Thank you to those who suggested the addition of 170lb to the right side. It works great. However (at least for me), changes made in "Aircraft Selector" or via the menu option at top of screen during a flight are not saved after the close of the MSFS session. Therefore the change must be repeated for each session.
Fortunately, a suggested method for making a change (as posted elsewhere by others) provides a "semi-permanent" version that keeps it in effect at least until a subsequent version of the aircraft is released. This involves changing a value in a single line in the aircraft's "flight_model.cfg" file.
To make that change for the JF Arrow III:
Navigate to "...\Community\justflight-aircraft-pa28-arrow-iii\SimObjects\Airplanes\JF_PA28_Arrow\flight_model.cfg"
Open the "flight_model.cfg" file with a text editor
Near the top, look for a line with "station_load.1..." in it
In that line, change only the "=0" to "=170", and save the file
This places a load of 170lbs into the right side
This one time change will be in effect whenever this particular aircraft is flown, no need to use the Sim's menus to make a change
If the new JF Arrow Turbos also drift, their "flight_model.cfg" can probably be changed in same manner
If this file gets corrupted, the Arrow can be easily re-installed, or a backup of the original file can be used to restore
Would be a nice touch if JF added a balanced initial weight option via the EFB
This change provided an important improvement for me. I use a joystick and throttle (Saitek X52), and I want to use the Arrow as a trainer in order to learn more about the Sim and aircraft before dealing with winds, engine pull, weight distribution, etc. Without the fix, the removal of my hand from the stick to make changes via a mouse (or KB) causes an immediate drift to the left, a distraction from the learning process. Of course not an issue for yoke owners who can keep the other hand on the yoke, or have/use rudder pedals.
After making the "flight_model.cfg" change, my enjoyment of flying the JF Arrow III went from "very high" to "Wow!". Now, realism can be phased in as desired.