Drying thick pecan in Nyle L200

[WDH]

Differential shell to core moisture content will also cause wood movement when processing, like when ripping a board into two pieces. 

[KenMac]

I'll typically turn everything off, including the fans, because they build up pressure and may evacuate more moisture which is not desired, and let things sit for 24 hours.  Just flip the switches and walk away for a day.  Just a nice, gradual cool down, and then probe again to check for case and core spread and also average MC.  The 3.3 % spread you are seeing is pretty high, your average moisture may settle to 8%  maybe 7%, which would put you in target. If the case to core values haven't tightened up, go through the reheat cycle with the vents closed again.

Differential moisture content causes wood movement as the values equalize, so it's best to try to get them in alignment now instead of after they have been planed or flattened.  

Thanks again YH. The main difference in MC I spoke of was between the thinnest slab and the 4x4's. I will certainly follow your advice. I plan to turn kiln off Monday morning. That will be about 84 hours at 150 degrees. Surely the core of all pieces will have reached 133 for 24 hours. 
I do plan to come visit your business at some point in the not-too-distant future.
Thanks to you also WDH. I am aware of case hardening and its'  effects on lumber.

[KenMac]

Well it's time to conclude this adventure that went much better than I was fearing. The customer picked up his pecan slabs and 4x4's last Saturday morning and was very pleased with the way it looked. Slabs at 26" wide showed little cupping and no cracking and smaller ones were even better. The 16 4x4's were not perfect but are plenty good enough for his purpose- posts for tables and beds. Total time in kiln was from !-18-21 to 9-11-21 and I never had to tax the equipment to achieve target temps and RH. Heat lamps did help getting to 150 for sterilization. I did overshoot target MC by about 1%, but I have learned how to prevent that in the future thanks to Yellowhammer and other very knowledgeable FF members who unselfishly assisted and advised throughout this adventure that I agreed to before I knew what I was getting into. 
 Thanks to all of you for your help and I hope other members have gained some knowledge from my experiment.  8)