There seems to be some interest on this forum on pulk building (four pages of responses to a question posed about the "best" sled to use in construction)
This is not a typical ultra-light project, but is a "niche" project; a sled designed to ride high in butt deep powder, to be used off-trail and can plow thru the tangled bush to reach the Holy Grail destination of your choice. You can pull loads large enough to support you for a 5-10 day trek.
Most sleds are based on the Paris expedition sled as is this one. You just can't beat it for durability. Most of this design was copied with permission from the "Michigan bushrats” with slight modifications. It is based on years of trial and error use in the remote bush.
The general idea is to make the pulk as snag-free as possible, thus removing the lips and adding flexible sides. Also, designing the front attachments so that it pulls up as you walk and that the brush has a way to travel down the traces and up and over the sled without snagging. Some members have made the traces so they breakdown and are removable, so they can use them as pickets to aid in the quick set-up of their shelters.
While the idea of pulling a pulk is not an ultra-light idea, this sled will keep those joints moving in the winter, when your choices are limmited to sharing trails with snow machines and skiers. There are many good designs for the trail walker that don't invole this level of fabrication. (but isn't that why we tinker)