Thanks for confirming the case of M500.. Yeah 😛 I ended up doing the M307 for H0 and H1 by hand and filling them up there and then doing the M665 and M666 as well. (I'll move them to the config.g since they don't really need to live in the override either.)
So far so good!
I'm all new to RepRapFirmware and coming from old Repetier 8 bit world. 😆