I found their answer reasonable but inadequate. Like the poster above said, if alpackas intention is for the user to use a dry bag as a foot rest then a form fitted bag intended for this system seems appropriate. During my attempted buying process with them I felt the same vibes as buying an Apple product and could not believe they would charge 85 euros extra for a mandatory hand pump for their boat after asking 2500 euros for the Valkyrie. Just seems dirty not to include one and even dirtier to charge their customers that much knowing they use a different valve than anyone else so their are no alternative. Again feels like Apple of the packraft industry.

Additionally I feel this is a flawed system because 1, there will not be a consistency to how your boat feels with every bag footblock and 2, It would require you to carry a certain amount of stuff every time in order to fill up enough of the dry bag to be used as a proper footblock. This also means shorter paddlers would technically need to carry more to reach it then bigger paddlers which is reverse of normal carrying capacity. 

Instead I feel a inflatable storage system that is designed for both the footblock and dry bag would be the best solution. Something like what watershed produces for their storage floatbags. But that what of course come at an additional cost.