By golly I think your on it Aisthesis. I think looking at the whole 1326 possible hands is the way to go since all are equally likely.
When I suggested finding the median best hand among 9 dealt I was thinking of sitting at a 10 player table, getting dealt my 2 cards and asking myself, what is the median best hand of the 9 remaining players? But looking at it your way, when sitting at a 10 player table, ask what hand you need for a 50% chance of being best at the table. Using your solution my calculator comes up with the hand ranked 99 out of the 1326 possible. Where do you figure that falls in the Sklansky ranking system?
btw, here's a link to a Heads UP Showdown Ranking system.
http://www.gocee.com/poker/he_ev_pe.html
How does the change in Ranking Systems affect the results?
PairTheBoard