Ive recently had this exact issue. I found that the following top layers worked extremely well. It might be overkill, but I took the settings directly from Slic3r. I have a I3 Mk2
Layer Thickness Top Layer Bottom
.05 / 15 / 10
.1 / 12 / 10
.15 / 9 / 7
.2 / 6 / 5
.35 / 4 / 3
Try this in S3D