Is there any way to tighten up the space between the grace note and the primary note of a flam in Sibelius to make it sound more realistic? Thanks.

Click and drag the grace note closer to the primary note.

Go to adjust note spacing and set the grace note space to .1 That's the same setting as the Tapspace template and it gives a nice tight flam sound. Then under that dialog select all and adjust note spacing! Voila crispy flams!