Ok, so if we take the approach of starting again, then in the absence of any presumptions re: high/low A, I'd look at the change from 4 months to 6 months of 2hr A time to 2:45/3hr by 6 months. Given that increase happens reasonably linearly, I'd just pick an A time around 2:20 or so given her age and use that as a base from which to tweak. The idea is to pick the A time, keep it consistent for several days then tweak as necessary based on nap signs.