Hmm. I just tried and this works here:

  hg qimport float_setting_callback_example.patch
  hg qpush

Does that not work for you? If you could copy and paste the error(s)
you get when you try to apply, that'd be good. It's really worth
spending a bit of time getting that to apply properly, because it was
fairly intertwined.

> There wasn't that much that changed so I
> was easily able to add the changes manually. I used the
> settingsedit.py that you provided as-is. The only change I made to
> settings.py was to bump the precision setting of
> 'RadioSettingValueFloat(RadioSettingValue): from 4 to 5.

Hmm, I didn't give you a settingsedit.py, but there were changes to
that in the patch.

Hmm, well I think I need to see your code to really understand all of
the above. If you could get the patch applied cleanly and then send me
the "hg diff" of your changes on top of that, I can certainly take a
look and try to figure out what needs to be done on the "set" side to
make it take effect.