We have just bought a Giant Peapod Duo bike trailer. DD is 7mo and can sit up pretty well and has good head control, but I'm now a bit worried about her being in the trailer and it being too bumpy for her. She's 15lbs. Ai can't seem to find any definitive info about how old they need to be! We plan to take it on cycle paths - both smooth Tarmac ones and ideally woodland ones. Any opinions welcome!