We adopted about 7 years ago. Since we were pretty sure that number 2 was not going to arrive, I had my LBS order for me a Trek Rocket. It was a single seater trailer that was very light. Once the little one could hold his head up with a helmet, we started to get out again. It was a hit or miss proposition, as we never n=knew how he would be. It still sucked pulling that extra weight, but what options do you have? Never really felt comfortable or even gave a thought to putting a seat on the bike. High weight and more potential for him to get hurt or cause issues if they shifted weight. More protection in the trailer. Now we have a triplet!