Q:

Three20 navigation without stacking

I usually avoid Apple navigation patterns, especially stacking views.  I tend to use one root view controller to hold other view controllers/views and switch between them so that when one is added other one is removed. 
What I'm trying to do is use navigation pattern similar to UITabBar, except I don't want to use UITabBar at all because it holds all its view controllers in memory. 
I'm familiar with Three20 Navigation Demo (the tab bar example), but can't seem to recreate it's behavior with preserving URL based navigation advances & not crashing.  I've played around with canContainControllers property without success. 
Seems that the new Facebook app (>v4.0) is having similar navigation pattern, so I wonder how they managed to do it. 

A:

I'm not a fan of three20 url mapping & TTNavigator as well, but as a framework, three20 still provides some great tools, especially the TTTableViewController and the UI elements.  
If you're looking for a nice url mapping, try Jeff's SOCKit - https://github.com/jverkoey/sockit
 Three20: [map from:@"twitter://tweet/(initWithTweetId:)" 
               toViewController:[TweetController class]];

 SOCKit:  [map from:@"twitter://tweet/:id" 
               toViewController:[TweetController class] selector:@selector(initWithTweetId:)];

SOCKit does looks more reliable and url friendly to me.