Just FYI for anyone reprogramming their Smallfry kit - Metalliqaz's EasyAVR software works great, and you're able to control in-switch LEDs:
Link to Easy AVR USB Keyboard Firmware and KeymapperIn the main Layout section in any layer, you can assign a key to :
BL Enable : turns in-switch LEDs on/off
BL Dimmer : 5 brightness levels for all in-switch LEDs
BL Mode : not very useful, but a couple of breathing modes
(To find these options, please read through the thread above, but the TLDR is to click on a key slot on the layout map, in the new box that opens up click on Key Assignment -> Scancode -> ... button, find BackLight functions in the bottom right section of the full possible function layout).
If you're too lazy to do this and want a premade .hex file for JD40 Mark II PCB to program with FLIP, here's a version for you:
(The Toggle Left Shift Function is mostly for the number row symbols, if you need to type out multiple ones in a row and don't want to press down Shift continuously).