I just pushed changes to support 64-row /32 panels to GitHub. It’s not packaged up into a release yet, but you can download the code. I tested it on the 64x64/32 panel I received yesterday.
@samy commented on poor refresh rate when driving with the Teensy 3.2: that’s to be expected, it’s a lot of work for the Teensy 3.2 to refresh a 64x64 panel, and it’s even more work when it’s /32 scan and not two 64x32/16 panels strung together. The Teensy 3.5/3.6 should do better.
I didn’t add @pinballsp’s changes to support V1-V3 shields as there are more changes needed. I don’t want to break support for any existing users by driving a new pin unexpectedly. I don’t have the time to wire up a 5th pin on my Teensy, so I wouldn’t be able to test the changes myself. If someone really wants /32 panel support added to the library, and you can’t make the changes yourself following @pinballsp’s code above, please ask. There are other SmartMatrix Library features I feel are more important, like adding APA102 support, and getting the library ported to a platform with WiFi capabilities.