Problem importing Civ V rifleman to BE, gun is not attached to hands

[HandyVac]

I'm trying to import bernie14's English Rifleman model for Civ V into BE. I've setup the art defines and a unit entry for the new unit, and have edited the model's fxsxml file to make it use BE Marine animations instead of Civ V Rifleman ones.

The resulting unit works fairly well, except that the gun floats in mid air above the unit's head instead of being attached to it's hands.

Spoiler :

I suspect this has something to do with the way the bones are set up/named in each model, but I have no idea how to fix it. Any help or advice would be appreciated.

Mod file attached.