It depends on the kayak but some of them are a lot harder than hauling a canoe.
The first year I did LRS solo, back when the course had 5 somewhat tricky portages, 'Bent was injured and bored so he built me an awesome, hinged, flip-over kayak portage system that was the envy of the solo field!
My new kayak is lighter, and I'm able to carry it upside down with the seat on my head. I do stick some padding inside my hat if I'll be doing longer portages though! The new LRS course has more portaging so it will be a bigger part of the strategy this year.