Thanks! His name is Rowan. So far, the only times he's gotten his feet off the ground very far, he made contact with the underside of the front of the seat, not with me. Perhaps if you had a really committed kicker or a truly lost-their-mind bucking fit they might be able to squirrel their way around it and get their feet up enough to get you, or maybe get you on the leg, but it seems like it would be pretty hard. But I will admit it's disconcerting being that close to the hind end of a kicking horse, even a tiny kicking horse!
Since I now know about him that this is what he does to lodge any sort of protest (he did it on the lead rope at the top of a steep hill he wanted to charge down, when I told him he had to walk it), I'm planning to add a kicking strap to my harness just as a precaution even though the behavior seems to be de-escalating at this point. I haven't logged much time in the Hyperbike yet but in comparison to driving a basic EE cart, I do find it very comfortable and so zippy! Not sure how it would compare in comfort off-road with something like the Cricket that has a real suspension. I don't find it too hard to get into and out of although it is really important that your horse has an excellent "stand" since there is a moment when you're standing between the horse and cart. I have experimented a bit with swinging my legs both around to one side and hopping on and off that way, which does work, but is a little more difficult especially when getting on.