Secondary fermentation: "cubitainer?"

[sentfromspain]

So I'm looking to get some more professional supplies, and I've been eyeballing these "cubitainers" and "Bags in a box"

The cubitainers would be a benefit, because I could:
-brew a batch
-leave it in the primary fermenting container for 10/14 days
-siphon out the brew into the second fermentation containers and leave the primary fermenting container free for the next batch that I would brew the day after.

And a further benefit would be that since they are made of a semi-rigid plastic, I could do half batches for recipe experiments (this way I save on supplies) and push out the air (to an extent).

My questions are:
-Has anyone tried out cubitainers?
-Would the cubitainers or bags in a box need air locks?
-As I generally leave my brews in the primary containers until bottling, I don't know how important it is to make sure that a secondary fermenting container doesn't have any air in it. Would I have to push out ALL of the air from the container?

 

[Wendy1971]

Yes no air in is a must. Is there no way of adding c02? i know they use these cubes in a box in the states alot to store and even dispense beer from.

 

[sentfromspain]

I don't understand that though, if beer can ferment in the primary container - and there is air in there, why would air being in the secondary be a problem?

I mean I understand that there is a co2 "protective coating" in the primary, but when you transfer to the secondary there should still be some dissolved co2 in brew. Also, the brew continues to ferment after the primary fermentation, so it still produces some co2...