Jesse's starting to do 180's in his cot.. but thats during the day when he doesnt have his grobag on. Ive found his grobag prevents him from moving which is great for him.
But ive seens others suggest to put those padding things that you put on seat belts, or something equivelant, on the bars so that if they hit them it wont hurt and then they can still get the air circulation through the bars. Might be an idea? Though you may need a few..