Ya I sent an email previous to ordering sans wasteboard to ensure the 1000mm X-Carve still came with all the neccessary support extrusions and this is the response I received:
All of the extrusions you will need, including those support members will be in the X-Carve 1000mm Extrusion Kit. The items you would be missing from the X-Carve 1000mm Waste Board Kit would be the waste board, threaded inserts, and the hardware to secure the waste board to the rest of the machine (pre-assembly insertion nuts and M5 X 20mm button head cap screws).
...there should be three pieces of extrusion underneath the waste board in the y-axis direction; two of them to the side and one down the middle.
So after I got that I just ordered some pre-assembly nuts and button head screws and I should be good to go! I opted out of threaded inserts since I'm not sure how I plan on securing my stock.