Here's information from a larger data set: http://www.powerscore.com/lsat/help/guessing.cfm
So what've we learned from this? If you have to guess use a C or D since based on the OP's research those average out to higher overall scores when guessing is required. Wish I'd of known that, my guess's tended to be random!
Took a PrepTest just by randomly guessing, ended up with a 131. That is good enough for a few Puerto Rican law schools.