I have the same coop. I had the same problem night one and two. I did remove the outer bar on night two. They kept flying up and nothing was there. They were rather confused, but they went inside. I removed the bar a couple more nights just in case. Now they go in on their own without issue and I don't have to remove the bar. I did rely on one of the roosters, he is the one that figured it out and got them in there. As far as room? They have plenty in there. They sleep real close together, so even if it was a box they would still be huddled together.
I never physically put them inside, I let them figure it out and they did.
I never physically put them inside, I let them figure it out and they did.