55 liters is huge. What are you doing? Snow camping? Hut trip? And where?
Carrying your boatd on that for any extended period of time is going to suck, a lot. Especially is you traveling below treeline and the trees get dense at any point.
A split might be something you want to look into.
I do have a 55 I use for hut trips and backpacking. It is the Osprey Switch 55+5. The design allows you to pull off a daypack or even just a hydration pack. Great for hut trips and snow camps where you are looking for lap runs. They don't make that pack anymore. If you can find one in condition on eBay, I'd recommend snapping it up.
It does have a board carry that works just how you want.
No - I have no intention of riding with it. It's to between bases on approach skis with my overnight kit.
I'll look out for the osprey but if anyone's got any ideas on a current backpack that would be sweet.