Bob (fundog): I was looking at the Giro helmets online--reading about the different brands available actually. I am looking to buy at least 4 helmets to have for guests to wear when I take them out on the sled. I would also have one for myself too. I do not skijor but I do bike and scooter with dogs and I wear a bike helmet then.
I have two "skateboarder" type helmets. One that fits without a hat underneath (summer and warm days), and one that fits with a hat underneath. Played with the removable/different sized foam inserts to make it fit well.
If your not having fun, you need to consider what you're doing wrong.
I prefer a helmet designed for cycling instead of ski or snowboard helmets. For skijoring i prefer a helmet that is well ventilated. Lightweight is nice too. If my heart rate is between 130 and 160 which it often is when I go hard then I worry more about my head overheating. Ever wonder why those XC skiers can go with such a thin skullcap when they ski in below zero conditions? Gravity skiers don't get their heart rate up for sustained periods of time. You almost need a warm helmet more for sitting on the lift. If I just want to work the dogs and not ski too hard myself then an unvented helmet would not be too hot. Honestly. I only use a helmet when skijoring at night to have a place to mount my light. I always use a helmet when I scooter or bikejor. A thin liner is all I need most of the time if it's cold.