Tyvek vapor barrier vest?

[roadpacker]

Hey all, I recently watched the Jay-P video here on winter layering:

http://salsacycles.com/culture/getting_dressed_with_jay_petervary

In it he talks about using one of two vapor barrier vests. I have a tyvek bodysuit that I cut the top off of to hopefully make a UL rain jacket, but it doesn't fit like I wanted it to, and now I'm thinking of cutting it down even further to make a winter vapor barrier vest. Wondering if anyone's tried anything similar. The damn thing isn't much use to me as it is so I'll cut it down and in the next few days take it for a spin and see how it performs. I'll let you all know how it goes.