I have the Gobi's and have the peacocks installed but would definitely put some of the camelback cleaning tablets through with a real good flush prior to using for drinking water. So yes I have yet to ever put liquid in them but for camping trips it would be a great idea. As far as the small fill hole you could always find a larger rubber grommet and drill out the hole further. I would be curious about trying to carry one full of fuel too but was always worried it might break down the adhesive that bonds the tanks together and that it would also leach through into the storage area of the gobo itself. So I use a Rotopak but am seriously looking at pulling the trigger on raid's under seat tank.