Mixamo Fuse autobiped provides unusable avatar.

I export my FBX from the Fuse website. I bring it into 3DS Max and I use the autobiped script provided by Mixamo. It runs and rigs myc haracter to a biped. I export the whole thing into Unity with standard export settings, leaving out animation.

I change rig to humanoid and then make a new avatar from this character, then I configure the avatar and I see this:

The top image is the default setup (though I did enforce Tpose as the thumbs were inexplicably not aligned). As you can see the arms are at the wrong angle. The bottom image shows what the setup looks like in max. Why are the arms lowered to a point below the model?

I had this problem a few months ago and somehow managed to fix it, but in my rush to meet a deadline I had no time to write down the solution and I'm back to square one on a new project.

Does anyone know if the problem is caused after export? Something to do with the bone names? A problem with Unity? Any clue? Annoyingly I can still access my Unity character from the older project which I got working and, when comparing various things I can't seem to find any difference in the set up that jump out at me.