Hmm, that particular Minitool Partition Wizard function requires a license ($60.) I'll try another route.
I found this on Source Forge: ext2fsd. It will apparently do all versions 2, 3 and 4. Is one better that the others for the AC66U? I'll try ext2 to avoid journal overhead.
Thank you for the pointer. I assume this John's Merlin Firmware fork you are recommending: https://onedrive.live.com/?authkey=%21AAkJBWoo%2DOiyKJo&id=9332FC159A7E129%215265&cid=09332FC159A7E129
What file system would you recommend if I need to swap large, 128GB flash drives, back an forth...
ASUS RT-AC66U w/ Asuswrt-Merlin 380.70
I could not get any exFAT formatted USB flash drive (2GB up to 128GB capacity) to auto-mount, whereas when reformatted as NTFS, all mounted and functioned successfully.