Here's how I did mine - not what you're looking for I know, but might give you some ideas.
First, make a cardboard template on the bike so you know it'll look how you want it. Then lay out the separate pieces on your sheet metal and cut out the shapes.
Bend as needed and weld together (I can't take the credit for this-my father in law is an expert welder!)
Think about how you're going to attach it...
Here's how it looks before upholstering
And finished
I built up the seat with closed cell foam and shaped it with an electric carving knife until I had the shape I wanted, then got it covered in vinyl locally. Total cost about 40.00 GBP ($60 ish?).
Oh, and the T bars have gone in favour of the stock bars and instruments now. Looks much, much better!