The extra bits of skin added with the ears mod doesn't seems to want to work unless the image is added to the image cache manually.

There needs special handling between Ears mod and this mod, as Ears mod needs to process the image and doesn't support higher resolution skins.
Without this special handling, two mods would be incompatible.

You should be able to just use the Ears mod unless you really need this mod...

after cecking it seems to only show when it in the cache and only in singleplayer

Good news is that while this mod is active it takes precedent over ears without causing any issues. While I have no idea what the intentions for implementing compatibly with ears is right now, I would like to at least request that this kind of non-conflicting override of ears be kept as long as possible.