There's a good chance you'll crack the frame....lots of people do this, much of the time it works, but cold setting a frame isn't a great idea. Why do it? It's not going to help you on your trip. Sure, the tandem wheels will be stronger, but the frame may be weaker.....bad trade off.

Relax and ride the bike the way it is. Will it break down? Who knows? Will it matter if it does?