My son is autistic and has come a long way since he was 4. He's almost 11 now. When he was that age, he really liked the feel of regular cotton. Not knits. He liked sweat pants, but seems more comfortable under a quilt than under his weighted blanket. We figured out that he liked the quilt top on the bottom and the backing on the top. I used about a 1/2" seam because I was a new piecer then and didn't want to mess it up. I made a top that was just squares. Then the backing was a VERY HEAVY corduroy. We tie tacked it backwards. He's almost 11 now and he loves that heavy blanket. A pressurized vest could be helpful. I suggest you talk to the OT some more. You could make a couple different ones and then the one she uses all the time would work. When my son was 4 he was non-verbal still, so I could only go off what made him scream versus what let him be quiet.