Custom cable for PXIe-6535

Hi,

I want to build a custom cable for a NI PXIe-6535 card : VHDCI for PXIe-6535 end, 4 subd9 for the other end.

If I take the SHC68-C68-D4 or the C68-C68-D4 as models, I come with 3 questions :

1) Is it necessary to build a 50 Ohms cable ? My signals will be 30kHz max.

2) Is it necessary to have twisted pairs ? If yes, can I build pairs with 1-2 pins, then 3-4, etc...

3) Is it necessary to have a shielded cable ? If yes, how should be the shield ? One shield per twisted pair, or one shield for the whole cable ?

Sébastien