I have no direct experience of the conversion kit. Based on
what I've read and heard, the kit accomplishes two things.
First, it lets you wear the liner while you're wearing the
poncho. Second, it converts the liner into a zippered
I've never tried to use the poncho as a sleeping bag. I use
it only in a hammock, and have given up putting anything
between me and the hammock that can be compressed.
It's certainly large enough to make a bag. It has tieout
straps all around the edges, so in a pinch you could tie it
into a bag and sleep with the open seam down. At least that
would let you try it out as a bag.