There’s a guy running a MN47 without liners with good success (200+ HP L28) I’ve showed my MN without liners to a couple of machinist and they thought the flow wouldn’t be that affected . It does leave a big gap under the seat which I would like to fill , but that would be almost impossible due to location. The rest of the port can be smoothed out . It does leave a massive port at almost 38mm at the port exit from the head . I think the MN 47 is best left NA mostly because of its small chamber