If you can get down to 1ft above drive head it could be very useful in some applications. I have had only limited success working with drive heads below 18" but if you could get it reliably down to 1ft drive the ratio would then be 2:1 and that is possible with care.

The standing wave needed to reverse the flow in the drive pipe needs to come from doing work on the delivery side, it may be that using rather inappropriate delivery valves will provide this with lower ratios, so part of this success may also be related to the delivery valve chosen.