Potentially very stupid question about Phil & Teds Sport

[hypnotisingchickens]

My hormone riddled pregnant brain is being utterly baffled, please help!
I bought a second hand Phil & Teds Sport, without a doubles kit. Toddler loves it, so will be perfect when DC2 comes along. I want to get a cocoon for the newborn - do I need to get the doubles kit and seat to be able to attach it underneath, or just the connectors and elbows (are they even called elbows?!) I don't want to end up buying loads of different bits only to end up with far too many permutations of seating!

Doubles kit yes, you need the second seat to attach on the top. Then the newborn lying flat in the main seat in the cocoon...

.... I believe you will need the elbow bits to attach the second seat on the top but I have no clue if they come with the doubles kit or not.

I'm pretty sure the "elbow" bits come with the doubles kit.
You'll need a double raincover as well - it then stretches right over both seats when the double seat is on the back.