I have the same question. My b is 2/3 the length of his bb bed and hits his head often when he tumbles around. Maid said we should buy bigger bed.
As our flat is small, we cannot buy 子母床. We are looking at bunker beds ( 2 levels), but there are no fence at the bottom bed. We need to buy fence separately or custom make a bed.
Hubby said bb is too young to sleep in a large bed and will fall out often. He said we should wait.....???
That is what we worry about....on more 'cage' to stop him from running around. What if he refuses to sleep at night and keep coming down to bother us? Any solution?