Having had a closer look at my Sextetts I thought of the following - provided that just having the self-adjusting headband shorter than the current minimum position would help you:
- as a first step, loosen the screws on the upper plastic knobs on the headband assembly which are limiting the adjustment range (the ones with L and R printed on them) and push them down so the band under the lower knob hits the silver ring and re-tighten in this position. If this helps, fine.
- if this doesn't help, unscrew the lower knob and move it from its round hole in the headband to go to the lower end of long slit next to the upper knob.
- Fold the piece of headband standing over the lower knob inside and adjust the upper knob so you get a correct fit.
This will loose most of the adjustment range but is reversible up to now.
If you're sure that the fit is fine for you, you can cut off the folded piece of headband and/or prolong the slit to the top for extra adjustment range - at least on my late production style headband (no holes in headband) there seems to half an inch of space until the metal inlay starts.
Joachim, who now has to undo the change on his pair...