Improving Operation of a LTD or Other Stirling Engine

[stan.hornbaker]

One of the commercial LTD Stirling engines has the piston concentric
with the displacer. The displacer rod passes through a plastic gland
in the center of the aluminaum piston. The dead space is mimimal. Now
if the displacer can be equipped with a snap action toggle, or
something similar the gas will be exposed to better heating/cooling.
Ivo Kolin did something like that in his "Isothermal Stirling Cycle
Engine" published in 1983.
How would you apply a snap or toggle action to a displacer?