That sounds logical. My internal res will be 12 qts. Was planning to make it hold 8 qts. That would leave about a 2" Air Gap.Is there any way that the float thingy can be modified to engage the refilling at a lower level, where the reservoir can be filled yet allowed to reach near empty before refilling? Or if keeping the reservoir full, is there an advantage to build in a larger air gap, after all if the reservoir is being topped up automatically then there is never any worry that the water will run out, and presumably the original air gap was simply to allow a minimum gap when full. It sounds like if the water level of the reservoir is being topped up constantly then you can choose the size of air gap that you feel is the most optimal. I wonder what size gap that would be?