Less starter...

Okay, during this last fiasco, I used almost 70% hydration, but used 400g starter (based on Jim's Sourdough Recipe).  I plan to cut the recipe in half, 500g flour, almost 70% hydration.  If I want to lower the amount of starter:

It will lengthen the rise time, right?

Do I have to compensate the lower quantity with more water and/or flour?

Steph