Absolutely great. I bet he loves the symmetry.
I have an autistic son too...he's 8. He likes to sit on the floor and listen to my sewing machine. He can pick out when my bobbin runs out long before I can. He says it sounds different. I've had this blasted machine for 7 years and I still can't hear it.
I made him a Disappearing Nine Patch for Christmas with his two favorite things. Thomas the Train and Mater from CARS. I'm hoping to get him to help me on some art projects I was inspired with from another quilter on this board. He's very artsy and I would love to get some of his drawings in fabric on the wall.
You did great.