Myron...that dash you made is first rate. I love it, especially the short overhang. Too bad you dont live in this area, a friend of mine is a GREAT tig welder. He could fuse it together in a heartbeat....aside from that the fasteners look hard core!
I gotta laugh.....2 4x8 sheets? Were you planning on making a mistake....or three? haha you must make things like I do!
On my 240SX track car I covered the inside door with aluminum sheet as well. Attached it with rivets so I can drill them out quickly as required.
If possible you might consider making a CAD template for the others to follow. Im sure it would be used often by DIYers.
On a final note you may want to lock tight the fasteners if you havent already.
Thanx