I would use a tether like you suggested, and I would rather trust my life to one of my splices than to some machine or commercial assembly line 'seam-ster'
If you handed me a 1/2 three strand tether with saftey locking clips at each end and a cow hitch in the middle, instead of that snapshackle and seizing. That way who ever is wearing it can adjust the lengths as they see fit.
Splice carfully, and use an extra set of tucks maybe too....
