The 140X140 board as used by SINAR and many other makes, is by far the most convenient as it is produced by a number of companies with any lens cut out size. So, is not necessaryto use Sinar panels. A cheaper version is produced by Horseman who also make panels for many other field type cameras and their lenses.
From your choice of possible cameras, you are intending to travel.
They are both lightweight large format and well suited to humping over rough terrain!
For what it is worth, my advice is to choose one make and stick to it. The Acra and Sinar, are faultless and stand supreme! Whatever your choice, whatever you build, good luck and stay in touch.