You should definitely feel the spin locks pulling the hardtop down securely in place.
Porsche TSB for spin lock install:
spin lock install
Part numbers (check to make sure they fit your model)
Left Guide 986 563 713 02
Right Guide 986 563 714 02
Bolts (qty. 2) 999 219 041 00
Take the hardtop off and check for the spin locks/parts. If you are not sure or can't tell that spin locks are installed, take it to the dealer or your mechanic. If they are missing order some, install them, then remount the top. I personally would not drive the car with the hardtop on and nothing holding it securely in place....
The hardtop will sit flush and should
not leak. If you do a search here there is a good thread that has some pictures comparing 2 hardtops; 1 with the gap and the other which is correctly fitted.
Here is a good thread showing where the spin locks go:
Spin Lock Question
Hope this helps get you started.