Here's a rough mock up of the aluminum member with out the trimming to bring it to within the dimensions of the original one.
The next time this pup is viewed by you'll, it will be ready to paint and mount.
Shaves 3-1/4 Lbs. Lots of work for little gain, but that's the game.

I just reweighed everything leading back to an original unmolested cross member and found the following:
Stock steel member weighs in at 5-3/4 Lbs with the trans mount on board.
Steel member modified and trimmed as you see on this thread came in at
5-1/4 Lbs with the trans mount on board.
The Aluminum member with trans mount on board comes in at 2-1/2 Lbs.
Like said above, not much, but I'll take it.