Question about center-line push-pull engine configuration

Hello all,

I am currently brainstorming/daydreaming of a twin design. I would
choose a pair of Rotax 912 or Jabiru 2200 or 3300. Considering the
place configuration of two engines on a twin, I am just wondering what
are the pros and cons of center-line push-pull design. There're far
less such configuration than side-by-side engine configuration among
twins, so I think there must be a reason.

The biggest (if ther's any other) advantage of push-pull design seems
obvious: the center line configuration eliminates the torque effect
when one engine fails.

So what're the cons? Besides the heating issue of the rear engine, I
can only guess it might be the efficiency issue. The front engine
disturbs the air flowing through the rear engine. If it's true, how
big is this disturbance? Say if the side-by-side two engines'
efficiency is 200, what's the possible number for push-pull
configuration, 180,160,150? If the number is no lower than 150, I
think it's tolerate for my use.

Thank you very much in advance.

Shin