The 1.75u space key in the spacebars kit isn't very useful. It's only used on three 40% keyboards (Vortex Core, Daisy, JD40), the latter of which actually requires two of them. As such, it can probably be removed from the kit. As for the second 1u space key, I'm not sure, but I think that one might be superfluous too.
It would be nice to see R4 1.25u Fn instead of Menu, since that key is currently missing from the kit.