Read This:
http://archives1.twoplustwo.com/show...ge=0&fpart=all
Tons of good info in there but I think this one part answers the specific question you asked:
"COMBO DRAWS
Odds of flopping...
20 outer (OESD + FD + pair): 0.077%
17 outer (Gutshot + FD + pair): 0.153%
15 outer (OESD + flush draw): 1.424%
14 outer (Pair + flush draw): 1.450%
13 outer (Pair + straight draw): 1.147%
12 outer (Gutshot + flush draw): 2.664%
------------------------
Total: 6.9% (1 in 14 times, 13:1)"
By the way you're wrong about the 10% chance of flopping a flush draw:
"REGULAR DRAWS
Odds of flopping...
9 outer (flush draw): 5.2%
8 outer (straight draw): 8.0%
-----------------
Total: 13.2% (1 in 7.5 times, 6.5:1)"
