[r-t] New doubles extents

[Alexander Holroyd]

On Wed, 7 Oct 2009, Richard Smith wrote:

> Something similar appears not to work in Carter because all three possible 
> double changes appear in both 'slots', and there is no single change which 
> contains places in 1, 3 and 5.

However, the Cramboing trick does work on Carter, and indeed on any 
in-course 60, as Robert Johnson proved a while back.

Ander