Can I weave 2/2 Twill Double Weave on 4 shafts?

No….you need 8 shafts to weave 2/2 twill double weave. The minimum number of shafts needed to create 1 layer of plain weave is 2 shafts…that is why you need 4 shafts to weave plain weave as double weave. The minimum number of shafts to weave 1 layer of a 2/2 twill is 4 shafts so if you want to weave 2 layers you need 8. 🙂