Faster clock speed, and expandable memory. Trying to future proof a little.
This is on my own board, and does not have an MCU plug into it. The firmware supports STM32, but not so sure about the config of the F411. I will need to edit the FW to support my pinout and my selection for SPI mosi, miso etc.
I also need to add some chips via hot air soldering.
I wanted a really small board as well. Idea is to bolt it on to the points box, in a simular way to a 123.
First thing is to do is see if it works at all.

Production is complete, and I'm waiting for FedEx to pick it up from China

Should be here by the end of next week

Edit
Subject to Customs of course
