another solution
I have used the old external frame hipbelt, but found it awkward with the hipbelt of the pack being carried when I pulled the sled.
I also tried attaching the sled arms to my pack with some luck. I used two biners on the hipbelt. I attached the biners to the wide hipbelt straps but not the padding. It worked okay, but you have to be careful that the hipbelt strap on your pack can take the load, most can't. My Gregory looked worse for the wear when I did this.
Another point. I found that the connection needs to have some floating. Meaning, it cant be a rigid connection or you'll be nagged by the load of the sled with each step. So I used a short section of cording to allow the sled to float. The length of this loop of cord needs to be tailored to your preferences. If you have it too short, you get nagging, if it is too long the sled rides up on you on the down hill. My preference is about a 4-5" loop though I've seen people who like 12".
If you attatch the cord loop to a point about 5" from the end of the sled arms then the ends of the arms will always be on your side and never poke you in the butt on the downhills. They do slide back and forth but you know where they are and with the 5" loop, they only slide forward up to 10 inches. Plus when you have the sled weigh against you on the downhill, it's nice to be able to gray the arms. I'd be bull__iting to tell you that you can steer that monster on the Chimney pond decent chute, but ...
JHS