DH & I would like to pack our five-month old in the Ergo and go for a ride on our trikes on smooth pavement. I've researched the issue and found that she won't be at risk for head/neck injuries due to slumping or a helmet too heavy for her little neck. The trikes are VERY stable - anything that would overturn one would be pretty violent (what I'm saying is that if you crash & flip this bike, you're probably getting hurt no matter what age you are and wherever you're seated. But most likely, this thing's not gonna flip - it has a very wide wheelbase & weighs about 55-60lbs.) She'll actually be in a semi-reclining position with her head on DH's chest as he wears her. So there - there's my risk assessment: the very low chance of catastrophic injury has been mitigated by the use of very stable bikes and a carrying system which places no unusual pressure on the child's back & neck.
We've checked local laws & helmets aren't required. Ergo-worn babies aren't addressed, but neither are recumbent trikes.
What haven't I thought of?
Me, my Sweetie , DD 1 (Dec 07), and DD 2 (Dec 09). Co-sleeping, delayed-vaxing, quia Lutherans!