I'm mixing a C-41 Fixer from scratch using the following recipe:

Water 110-120F 800 ml
Ammonium thiosulfate 60% 162 ml
Sod. Sulfite anhyd. 24 g
EDTA Sodium salt 1.25 g
Sod. Bisulfite anhyd. 12.4 g
Water to make 1 litre

I'm substituting Sodium Thiosulphite for the Ammonium (I understand this will be a slower fix time but have no choice)

So 2 questions:

1. Does anyone know what quantity of Sodium Thiosulphite I should use for this recipe?
2. How long should my fix time be?