That's great. Welcome to the hanging crowd.
On the undercover, I would not use sil-nlyon. It is not going to breath and cause a lot of condensation on the bottom. You are going to want something breathable.
Are you going to make an undercover as in something to block the wind and trap in dead air or a down underquilt for insulation? Either way post pics for everyone along the way.
Is that too much to ask? Girls with frikkin' lasers on their heads?
The hanger formly known as "hammock engineer".