Would the real W frame please stand up.

[Rudolf]

When it comes to dipole bass, W frames are recommended as a compact alternative to large OBs and H frames. On closer view I see 2 claims that most everybody (including me) seems to take for self evident, but that I haven´t seen backed up by published measurements:

First:
Linkwitz recommends mounting the drivers so they are facing the same direction but moving in opposite directions., so one cone is moving towards it's magnet structure wile the other is moving away. This should reduce second order distortion by cancellation.
By doing this, both drivers are working on very differently shaped air volumes in front and back. Isn´t this asymmetry a new (and worse) source of distortion? I believe there is an audible difference – but to the better or the worse? Has anybody gathered hard facts regarding this?

Second:
Does it hold true that a W frame still has a 8 radiation pattern like a H frame? Or is it more like a cardioid or something else? Could anybody point me to VALID polar measurements of a W frame (with mic distance >1 m from W frame) that shed a light on this?

Thanks
Rudolf