Yeah, your first time cutting hatches can test your nerves... I still want as little gap as possible. So I lightly sanded the edges of the hatches just to knock down some of the saw marks. This gave me enough clearance with an application of epoxy. Try not to change the contour of the edge ( ie sand flat), if you have a little wave in the edge, or if your cut is not perfectly straight. Your eye go right to any gaps in the hatch and deck space more than seeing a wave in a cut.
K.Greer