Am I reading right that this cannot be done without digging a hole to make room for the drop?
The only way to know for sure is to get the shaft free from the coupler and see if it clears the rudder coming out. On mine I needed to dig about 18" deep to get enough space for the rudder shaft to clear the hull. That said my boat was on jackstands so the bottom of the keel was 1.5" above the ground. If you are on a cradle or trailer there may be enough clearance. Measure from the rudder tube from bottom of the cockpit to the hull and compare to the rudder height off the ground.