Forget about one sheet 9' X 5'6".
Consider getting two 5' X 5' X 1/2"sheets of Birch multiply.
Slice 6" off one edge of each 5 X 5.
Remove one 6" X 6" end from each 5' X 6" cutoff.
Attach one 4' 6" X 6" remaining cut off to the new 4' 6" edge of each sheet.
You now have a pair of 4' 6" X 5' 6" halves which can efficiently make your 5' 6" X 9' panel.
The two 6" X 6" cutoffs, slice them up in 1 1/2" X 6" strips and mount then alternately on the two joining 5' 6" mill edges for joining fingers.
Earlier assembly shown below.
Adjust #s for blade thickness.