T- and D-flapping when at start of word preceded by vowel

Yes, that d flaps in my casual speech. I think what happens is that the following vowel loses its stress and this shifts the d into the preceding syllable, making it subject to the flapping process. If that's right, an initial t in a word whose first syllable is unstressed should also flap. We can test that with "I'll go tomorrow/today". Those t's flap, for me. But here's one that doesn't: "He's so tyrannical!" (perhaps because I wouldn't use that word in informal speech).