  Renewed interest in circular e+e- colliders has spurred designs of single
beam-pipe machines, like the CEPC in China, and double beam pipe ones, such as
the FCC-ee effort at CERN. Single beam-pipe designs profit from lower costs but
are limited by the number of bunches that can be accommodated in the machine.
We analyse these performance limitations and propose a solution that can
accommodate O(1000) bunches while keeping more than 90% of the ring with a
single beam pipe.
