I was inspired looking at Atari 2600 Xonox Double Enders:

http://www.atariage.com/label_page.html?LabelID=49

Two games in one with a flip!

Now, I know somebody out there has plastics working experience...

So, it would be awesome to see NES double-ended carts, like SMB 1 and 2, or Zelda 1 and 2, or Megaman 1 and 2 ... you get the idea!

Unfortunately I'm lame at both plastics work and electronics or I'd do it myself.

Any takers?  It's kinda one of those pointless projects like the world's largest NES controller, but somehow fun to think about at the same time!

way cool idea

but i also have no plastic handeling experience

Not sure that idea would work in a regular, not toploading, NES... it would be nearly impossible to remove the game from the console after playing...

Yes it would either have to be a top-loader or a front-loader modified so you don't have to press down to lock in the game.  I think if it was longer you'd be able to get it out of the front-loader ok.  The Xonox carts were intentionally made longer than regular 2600 carts to make it easier to get them in and out of the system.

There are already NES double enders......well kinda.  Hydron makes a few carts that are NES on one end and fami on the other.  In other words, one is 60 pin, and one is 72 pin.
~~NGD

Sounds a lot like Hydron carts, which had 60 pins on one side and you flipped to the other for 72 pins. Perhaps Hydrons could be more easily modified to have 72 pins on both sides. Might not fit two NES boards, but would easily fit two Famicom boards.

Beat you to it JC ;)
~~NGD

I was thinking Hydron too... I even have 2 Hydron carts sitting on my desk right now :-P