On the topic...
The domes are pretty easy. so long as you don't want something that won't fit in your oven.
Clear acrylic sandwiched between two bits of ply with holes cut in them.
In the oven on max.
Pull out when the dome has sagged to the point you want it to.
For bonus points, just put a hole in one sheet of ply, put it on top and run a bead of sealant between the acrylic and the bottom sheet.
Into the oven and, when hot, blow some compressed air between the acrylic and the bottom sheet.
I once made a 1m diameter dome from 6mm sheet like that....
As others have said though, the dome only provides a small improvement, and may not be worth the hassle.
As for the ducting. Hit the aircon places up for scraps. Not quite as internally reflective as the light pipes, but the price is right...
