I agree with you John  - this is just not a common problem with the Pluribus system except in cases where the operator has a problem with a guidance system or staying awake....

However the situation described above is a different type of strip and sounds similar to the old Nebraska ridgetill problem of how to keep the planter on top of a "ridge" that it inherently wants to keep falling off of to one side or the other.

One low tech and relatively low cost thing you can do to a drawn planter is to add either 2 or 4 (depending on the size of the planter) "Stabilizer coulters" to the planter frame. These are large, rigid straight coulters that are bolted to the frame of the planter usually set to run in the firm (=compacted) tractor tire paths. They go in the ground maybe 4-6" deep every time you lower the planter. Hawkins Manufacturing in Holdrege NE is one source.

These stabilizer coulters act like the keel on a sailboat and help to keep the planter from sliding sideways. They help the planter follow the tractor better.  They are sometimes used even on mounted planters in ridge till areas.

Even a mounted planter can not be set completely rigidly to the tractor especially if you have any curves or anything but dead straight rows. You have to leave a little room at the sway blocks or chains other wise every time you touch the steerign wheel with the planter down you will be trying to drag it sideways. This is especially true on a tracked tractor where the 3-point moves sideways everytime you turn the wheel.

Stabilizer coulters may help but frankly I just have not heard of this as much of an issue with the Pluribus. Making a good strip is sometimes a challenge. Staying on it with the planter, EXCEPT in areas with extreme side slopes and curving rows, is usually not a problem. jmho.

Jim at Dawn