It saved our lives today hauling an Otter Magnum sled into a remote lake (probably similar to your own adventure). It makes a HUGE difference when you are pulling the sled by hand. On hard pack snow or ice, you can pull it with a couple of fingers. It will let you go places you simply wouldn't make it through even with a little jet sled.
Don't use smaller than 2X10's for the uprights...the idea is to get the sled up out of the snow so it's not plowing. Use downhill skis rather than cross country skis as the added surface area works much better by all accounts. You're going to want to mount your rope to the front of the Smitty sled as you'll always be pulling it, except up the steepest slopes that no single person can pull it up regardless. My son was pulling ours while I pushed it for the first couple hundred yards up a steep winding trapline this afternoon. Once we got out of the trees to a more moderate incline, he went back to pulling it by himself while I tried to decide whether I was having a heart attack or not. We went through that trapline 40-50' at a time for 45 minutes. Yes that's an Otter Lodge hub I'm packing on my back for good measure. Cross-training HIIT millennials...
One other tip, put eye bolts on the front and back uprights so you can cross-strap the sled onto the smitty sled. If you pull it on steep hills, the sled will want to come off the Smitty if it's not attached properly. Shoot me a PM if you want some pictures or to discuss further. I've used one for the same terrain you're intending.
It looks awesome... Smitty sled plans are very cool...
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