I´m not sure it would much matter, but in principle, the displacer dwell times with this kind of linkage would not be symmetrical. The displacer would be snapped up very quickly, and then slowly lowered down. Gamma Stirlings are actually "double acting", in the sense that both the overpressure of the expanding heating air, as well as the under-pressure of the shrinking cooling air, are both utilized. Both drive the power piston to the desired direction. Although not by the same force. The suction is usually weaker, because of the lesser temperature difference. With the usual crank arrangement, both strokes happen in +/- equal time spans. Here that would not be. The displacer would be snapped high, and held high for longer than on the cooling side. I believe that would lead to a higher overall temperature and pressure in the engine - not necessarily a bad thing at all. Heating would happen for a lot longer than cooling. I really can´t say if this arrangement, where there´s more time to heat the air than to cool it, would be of benefit or detriment! In a slow running LTD Stirling, it might lead to a non-runner, though (an even air temperature in every part of the engine), unless there would be something cold (ice, evaporating liquid, cold water, etc.) above the displacer. But then it would no longer be an LTD... Nothing like experimenting, though!