Castings are typical in the mc16 and mc18. The later mc21 and mc28 are less pronounced. When you spit the case you can use a rotorary tool with a sand drum to smooth all the rough spots.

As for rear shock, the stock is fine but the spring is for a 120 lb kid. So when I was doing the cost trades I just got a Nitron with a spring to take into account my 180 lbs plus leathers. Had I delayed the purchase I might have gotten an Ohlins, but overall I'm very happy with the Nitron. Obviously this makes it non OEM.