With the Churn Dash block, the center stays at 5", the half square triangles are 4 1/2" and the remaining two patch block is 4 1/2" X 5"!! This means that you can make two half square triangles blocks from two 5" squares and two of the two patch blocks from two 5" squares.
Why am I talking about Churn Dash blocks? My Crosswise quilt is made from them. However, I used a different color placement than the traditional block and actually created a Greek Cross block unbeknownst to me at the time that I was messing around with the pieces of the block. Whatever you call the block, I'll be doing more variations of it because the nickel squares are perfect for it!