Hopefully these two videos will work one is the how to load and fire the cannon the other is a fun video of what its like to be a cannon ball.
Step 18: Measuring for Cradle Sides Anchor
Decide which end you want to be the front then measure the 1st mark 2" from front of cradle @1-3/8" in from side. 2nd Mark 8" from front of cradle @1-3/8" in from side. Mark the opposite side of cradle on the same face with two more marks at the same measurements.