Help: Import/Export custom weapons into dev kit

Firstly, I am a complete newbie to blender and the ark dev kit. THe aim is to use the metal axe/hatchet as a base to make a sledgehammer, which will be purely for getting stone.

I watched this tutorial by FancyFlannel first:

I used Blender instead of Maya because that’s what I had access to. I managed to remove the hatchet mesh and replace it with the one I wanted (a sledgehammer) and parent that correctly to the root skeleton/armature.
Then in Blender I clicked on the hatchet_jnt then RMB the mesh, and weight painted it. The hatcher comes in TINY though the bones are miniscule and I was clicking them in the “explorer” style options window in the top right. I painted the mesh with a weight of 1, then saved it as an FBX. When I import it into the dev kit I get this:

The texture you are importing is not a power of two. Non power of two textures are never streamed and have no mipmaps. Proceed?
said YES

FAILED TO MERGE BONES:

This could happen if significant hierarchical change has been made

  • i.e. inserting bone between nodes
    Would you like to regenerate Skeleton from this mesh?

WARNING: THIS WILL REQUIRE RECOMPRESS ALL ANIMATION DATA AND POTENTIALLY INVALIDATE
SDaid NO

after that I get this error:

Warning: no smoothing group information was found in this FBX scene. Please make sure to enable the “Export Smoothing Groups” options in the FBX converter plug-in before exporting the file.

But in Blender when exporting, I can’t find anything that looks like that.

Could anyone please tell me what I’m not doing correctly to get this working?