LindsayPatten

As a follow-up in case anyone else runs into a similar scenario:
 
After reading more about the causes of delamination/layer separation I found out that residual stress (aka internal stress) caused by material shrinking as it cools scales with the size of the print.  For any given set of number of perimeters, infill, etc., there will be a maximum size that you can scale the model to before residual stress will cause problems.  As a model gets taller the heated build plate can't heat the whole height of the print so that doesn't help.  So it's not surprising that even when I got everything working at half scale there were problems when I printed at full scale.
 
In my case increasing the wall line count was how I got a successful print.  Increasing wall count for the whole model added too much weight so I used support blockers with per model settings to only increase it at the leading and trailing edges.  The model has 3 wall perimeters generally and I still got a small delamination  adding 3 additional wall layers on the leading and trailing edges so I gave 5 additional walls a try and that was successful.  I should try 4 additional walls but each model takes almost half of a 1kg reel and I've wasted multiple reels already so I'm sticking with 5 for now.  I'm still a little surprised that three additional walls, for a total of six, was insufficient but I guess it goes to show how strong residual stresses on large parts can be.  The model is 247mm tall and 358mm long.
 
I also added two-layer "mouse ears" at the bottom to combat warping away from the build plate as brims alone weren't strong enough to stop that.