Ordered and received some W25Q128 chips from Digikey to give the Black Pill another 16MB of flash memory. First I soldered on the decoupling cap. The pads for the it are 0402. The smallest cap I had was a 0603. It fit - barely. Then I soldered on the chip. No problems. SOICs are easy. Here it is still gooped with flux.

Cleaned the board and now it looks like this. Much better!

Then on to the software. I made the mods to mpconfigboard.h from mcauser's git page and built. It errored out with this:

oards/WEACT_F411CEU6/bdev.c:16:8: error: unknown type name 'mp_spiflash_cache_t'
  16 | STATIC mp_spiflash_cache_t spi_bdev_cache;
     |        ^~~~~~~~~~~~~~~~~~~
boards/WEACT_F411CEU6/bdev.c:23:6: error: 'const struct _mp_spiflash_config_t' has no member named 'cache'
  23 |     .cache = &spi_bdev_cache,
     |      ^~~~~
boards/WEACT_F411CEU6/bdev.c:23:14: error: excess elements in struct initializer [-Werror]
  23 |     .cache = &spi_bdev_cache,
     |              ^
boards/WEACT_F411CEU6/bdev.c:23:14: note: (near initialization for 'spiflash_config')
cc1: all warnings being treated as errors
make: *** [../../py/mkrules.mk:77: build-WEACT_F411CEU6/boards/WEACT_F411CEU6/bdev.o] Error 1

Awesome! Now what do I do? Scratched around on da web until I found someone with the same problem. RaulKompass. He knew how to fix it. His instructions have one error: he accidentally writes that you should modify mpconfigport.h. The file name you should actually modify is mpconfigboard.h. There was some brief confusion, but I figured it out. Thank you RaulKompass!!!

After making the two changes he suggested I built again. It finished successfully and flashed the board. Victory is mine!