I aim for the center of the board and use a 12 gage deer slug and that usually does the trick.....
Wear safety glasses too......Seriously when I shoot using my board a couple of things that helped me out are as follows:
1) Be mindful as to how you hold the plane and use consistent pressure throughout the entire stroke. Like martial arts and golf target your stroke through and past the board and not end to end.
2) I discovered that when I am getting gaps they are often caused because the surface that my plane rides on is not perfectly level/flat. So these days I have a shooting board that I check with a straight edge when clamped in place and shim it with some number of post-it-notes until the plane surface is level. My results improved dramatically as a result.
Good luck.
