A question about spectral leakage
I see you've already accepted one of the answers, but you (or others) might be interested in: R. J. Webster, “Leakage Regulation in the Discrete Fourier Transform Spectrum,” Proc. IEEE, vol. 68, no. 10, Oct. 1980, pp. 1339-1341. -- Among the statements:

"A point insufficiently emphasized in the literature is that leakage in the DFT spectrum is a phenomenon of calculation.  The continuous distribution of leakage energy is determined only by the form of the window, and the DFT is a kind of lattice through which this continuous function is observed.  Because the lattice is fixed by convention, and the leakage distribution shifts according to the frequency of the signal, the discrete leakage components become dependent on the signal frequency."

(regarding the familiar 'picket-fence' effect): "The reader should note, importantly, that this effect is not a property of the harmonic nature of (the signal frequency fzero), as seems often suggested, e.g., [5], [6], but of the essentially arbitrary way G(f - (the signal frequency fzero)) is evaluated.  The apparently special relationship between harmonic frequencies and the rectangular window, in which the zeros of the window transform coincide precisely with the DFT sampling frequencies, is neither significant nor unique."

The author then goes on to show an example of using a shifted sum-of-cosines window centered on f = 10.25 that reduces the leakage to zero beyond bin 11 of his FFT when given an input signal of that frequency.