I was looking the clean Stream

http://www.platypushydration.com/product_detail.aspx?ProdID=29

I noticed in the photos that the 'clean' bag was used in an upright position - Would this not slow the flow? It appears that the water is filling the bag from the bottom up and would have the weight/pressure of the water that has already filtered above the in flow point.
Can those bags be flipped upside down? it just seems to make more sense to fill the other way - but then there would have to be no air in the bag.

Side question - can the ceramic filter from an msr miniworks be used to gravity filtering without having touse a super long hose and great distance between the bags toprovide enough pressure to force water thru the filter? I just want to know about the filter - I have already solved the problem of having a housing for the filter cartridge itself.