justabit = I dont know if this will be of any help to you are not but I did a recent analysis of Doubles for my Texas Midday database. With over a years worth of input I found these facts:
1. What plays still has a Sum Total 11-20 more then 0-10 or 21-27. Is only 2 times as many as 0-10 and Sums 0-10 only about twice as often as Sums 21-27. Three different digit combos seem to Sum 11-20 on a 2 1/2 times as many times as Sums 0-10 and Sum 10-10 a 3 to 1 over Sums 21-27.
2. Unlike 3 different digits having a 2/1 split on Level of Play, more Doubles come from within the most recent 4 games then a 2/1 split with 2 digits from most recent 4 and 1 digit 5 or more games out. There still isnt an abundance of 1/2 splits either where the digit that doubles is the coldest number. Overall, still the majority of the digits that play in a Doubles game comes from within the last 4 games whether it be a 3/0 or 2/1 split.
Sorry I dont remember what the results were regards repeat digit.
demdev= is your question regards "tracking down" numbers in general or Doubles? I do maintain a separate Database for Doubles/Triples Only and I treat the numbers the same as I would a database that had all the numbers. The same things I consider in tracking all combinations I apply specifically to Doubles/Triples Only or any other specific tracking I do such as all Even Games or all Odd Games.