Defective flooring . A rear floor slot for the back panel was damaged..
So, I decided to use the floor panel anyway, because it took over 1 month to get my 7 X 7 SUNCAST VISTA SHED to arrive at my home.
Sofar, it is rain proof .. To make the base of the shed  more stable. And better windproof , I used several L   with screws in the inside , inorder to make more support to the floor, and to the sidings on the back, and to the 2 sides. (The L were steel L ‘s , that are used to beef-up Shelves in Bookcases .)
This is the second Suncast Shed that I bought, and put together by myself..The first one deserves 5 stars.
The first one was smaller, and used for the storage of clothes..And, supposedly, can withstand higher winds.
The second one( 7 X7 Suncast Vista) is for the tools toostorage of tools, lawn equipment and lawn mower.