After upgrading from v4.0.2 to v4.1.0 elasticity stopped working. After some research it turned out that following the call to cpSpaceNew I had to add this line to restore the original behavior:

space->elasticIterations = space->iterations;

I suggest that by default cpSpaceNew should set both of these iteration values to the same original default of 10 and a new API be provided to create a space with alternate values. For example:

     cpSpaceNewWithIterations ( int iterations, int elasticIterations)

In the trunk and hopefully soon to be released version of Chipmunk it defaults to the old unstable stacking behavior for elasticity when elastic iterations are disabled. Sorry it took me so long to get to this as I had not set my preferences to receive notifications of issues being added here.