I'm close to trying the calibration file that improves 2.4GHz, and can probably do this by "trial and error," but rather than land on the side of "error" instead of "trial," I'm going to ask first just to be sure 
This is what I have on my router:
root@EA6350v3:/lib/firmware/ath10k/QCA4019/hw1.0# ls
board-2.bin firmware-5.bin
The openwrt-1.02.oc-23c228.tar.gz source tar ball has a file called "board-linksys_ea6350v3.bin" in each of these sub-directories under the "calibration" directory:
$ ls
ah_Y9803 default fcc_Y9803.au_Y9803 hw_1_Y9803
art eu_Y9803 hw_1_DK01 hw_1_Y9803.ic_Y9803
au_Y9803 fcc_Y9803 hw_1_DK01.au_Y9803 ic_Y9803
And now for the dumb questions....
Is "board-2.bin" the 2.4 GHz calibration file on my router?
Do I just replace "board-2.bin" with "board-linksys_ea6350v3.bin" (renaming it to "board-2.bin") and reboot to try out a new calibration file?
Finally, which calibration folder has the "board-linksys_ea6350v3.bin" file most likely to improve 2.4GHz?
Thank you!