Finishing Cast Iron With Facemill – Wiper insert?

Hi. I feel like this is kind of a dumb question, but after talking with my boss, we were in a bit of a disagreement on the use of wiper inserts.

I have a Iscar facemill with 6 octogon inserts. We are running a cast iron exhaust manifold and need to hold a decent finish (63 micro) on the gasket surface.

He thought that you put 1 wiper insert in the facemill with the rest regular inserts, the single wiper insert does all the finishing. However, 1: I’m already using a separate roughing facemill, leaving only about .010″ stock, and 2: I feel like it would take too long.

Manifold surface is 3.5″ wide and 25″ long, obviously an interrupted cut.

Upon googling, I do see some people say 1 wiper, the rest standard. But I’ve seen a wiper-only suggestion too.

What do you guys think?