My thoughts are to run a cord or thong through the binding hole of the cross bow and attach a large D ring to it. Lash another D ring near the butt. Hook ends of a strap to my armor about the same place my shoulder straps on my weapon side attach. Running loosely through the rings the strap would hopefully allow me to move the crossbow enough to load and shoot while allowing me to 'drop it' to throw hammers or work a ballista.
I don't want the strap running around my neck so I don't get strangled in some sort of press / mound of bodies.
Has anyone else experimented with crossbow slings? Other option for the butt of the crossbow is to copy the butt sling attachment of a Mauser 98.
How about a sling fixed firmly to the crossbow and attached to rings on my armor?
I have to imagine a crossbowman of old had some way of slinging a crossbow on the march. Did they use some sort of case or bag to protect it in nasty weather? Any ideas?