I did some modifications on a burley flatbed for my girl in the day. Thing is we could be gone all day, can't imagine her running that whole time and having a trailer guaranteed I would get her home. There may be a " window" of time in a dogs life where it may be able to do that but in dog years that's really not a huge window. As my dog aged she still liked to go out and I liked having her with me. She did jump from side to side with excitement which did make the trailer jump around but that was something we learned to deal with. There was also a time the trailer tipped and she ended up on the ground. That freaked me out. There were other people around the saw it happen of which I asked them their opinion, please be honest, did she do something or was I going too fast ( it was also during a turn) and one guy said after a short pause said he thought it was my fault. I thanked him for his honesty and never rode fast again making turns. I can't see the trailer flipping over if just moving in a forward motion but turning is another story. Looking back, my girl missed her 15th birthday by 5 weeks and that trailer performed flawlessly allowing me to always let her be a part of my world, not just when I got home. Those were the days.
J