A quick question, do you have a weather seal between the two halfs when they but up together or does the overhang provide enough protection combined with the roof angle.
That was my thoughts exactly, im from northern territory, and let me tell you that sometimes no amount of overhang will protect from water getting in, especially when backed by a nice stiff breeze! if it was me ide be making something like a weather strip from a door to flap over. Just like heat electrics and optics do not fare well with water! so soft and smooth is dear water but so ever harsh!
You are all correct. Even though nearly all rain in Melbourne comes from the south west it can give nasty surprises.
I intend to put a flat piece of flashing against the bottom roof top edge and seal it with silastic to form dams at the top of the valleys. The upper roof will have flashing that covers its top end and just clears the lower roof. This will ensure the drip line from the upper roof is well down the lower roof.
In image one the lower flashing would cover the visible timber. In image two you can see how well this would all mate.
Water can flow uphill with the wind behind it and get in where you least expect.
After a full summer the hottest the inside got was about 4C below outside temperature. Even on the worst day where it was 47.5 outside it was only 43.2. That was black Saturday.
Normally the inside temperature is well below outside. It is only sustained hot days that the inside temperature is only 4C below.
The natural cooling of having a wooden porous deck and a well insulated roof really works.
The good thing is once the roll off rooves are opened, every thing is at ambient very quickly.
if it was me ide be making something like a weather strip from a door to flap over. Just like heat electrics and optics do not fare well with water! 
so soft and smooth is dear water but so ever harsh!
