I think there is another link where Kaeko goes into detail about his various tests (it should be from that thread or in that thread). My understanding is that he started out with rank 1 DoL for 1 point stone throw vs. marmots and worked from there on various theories.

The early tests were like: stoneskin 2x rank 1 DoL, have one pull a marmot with stone throw. have the other hit it with stone throw until it moves (takes 2 stone throws, missed stone throws have no impact, ...).