Great questions.

PM me if you want early access 
I’d at least try it out, if it doesn’t work our other monthly adjusting schedule is definitely an option.
Here are some tips on adjusting flex if it is not performing how you expect.
Precip will definitely help with zone durations. Area is only used for estimating water usage, and does not impact frequency or duration.
No, but the closer your precip in./hr is to actual, the more accurate the runtimes. With 2.6 we also allow you to adjust zone durations at +/- 5% increments if you need more/less watering.
I can get you the software now if you’d like. Just PM me iOS or Android and Apple or Google login email address.
If you have accurately input your precip in./hr and an accurate yard area, then it should be very close.
Gen 2 also supports a flow sensor for deadly accuracy 
Hope this helps.
