"So (and now, I *am* pulling some #s out of my ass), I'd expect a the score in a 10-game blitz match to be something like 5:5 or 6:4 in favor of the 2600, and the score to be something like 3:7 in favor of the 1700 if there was a longer control."
Of course it depends of the strong player you are speaking of in blitz (some IMs are very good blitz players like curtains, while others are not). I think your estimates are pretty reasonable on the whole though, certainly the score would be closer in blitz than regular chess. My guess of 95% might have been a tad high, but I'd be very surprised if it was lower than 80%. My guess is around 85% in slow chess, 65% in blitz. If you want some other action, I'm still willing to take curtains on in equal material at 3:2 time odds if you or anyone else is game