What's the obsession with having your starter double in size? I haven't heard about it before.
I'm feeding my starter by weight, so that I can take the same amount out when I bake, and the volume of growth really doesn't come into play.. I mix in whatever I have, mostly rye and spelt, sometimes wholegrain wheat, but it hardly ever doubles in volume and the bread comes out fine at the end of the process.
If you have a nice range of bubbles sizes forming in your newly mixed starter, you'll be fine.
I'm feeding my starter by weight, so that I can take the same amount out when I bake, and the volume of growth really doesn't come into play.. I mix in whatever I have, mostly rye and spelt, sometimes wholegrain wheat, but it hardly ever doubles in volume and the bread comes out fine at the end of the process.
If you have a nice range of bubbles sizes forming in your newly mixed starter, you'll be fine.