It applies successfully and if I do it through dconf, it’ll still show as “flat” even when it’s reset to “default” and the accel is back on. That’s the whole thing: the dconf user file stays flat as I want it to, but the actual behavior does not. So that’s a bust, same behavior as tweaks where it says flat but reverts to accel. Where should I look for the config tweaks / dconf are editing? Running chown recursively on my config folder didn’t change anything. Note that other settings in tweaks will stay permanently, it’s just this that resets.
Also, unfortunately piper does not support my mouse, a Logitech M570 trackball. I would just put it on the mouse like ringo suggested, but I’m able to get it perfect with the flat profile…it just never stays that way.