I just completed a Stihl ms660 and ms460 build/woods port a few weeks ago. Turned out great. I dropped and tapered the lower transfers to the base of the cylinder. I also angled and smoothed the upper transfers toward the intake side of the cylinder. I widened, raised, and polished the exhaust port. Removed the casting ridge in the bottom of the intake port, along with the other casting turds left in the intake. Gutted the muffler basket, opened up the stock side port, and bolted on a factory dual port cover. I opened up the exhaust opening just a bit on the cover too. I didn't monkey around removing the cylinder base gasket, or milling the cylinder base. I don't have access to the tools do that. Plus, all high quality pro saws (Stihl, Husky, Jonsered, Echo, Dolmar) manufactured today all have high compression engines. That's why these manufacturers recommend minimum 91 octane fuel. Why spend all kinds of time, money, frustration to raise the compression another 5-10psi on a work saw? I also removed and polished the casting turds/lines from the piston windows. Both saw turned out great. Power and acceleration beyond belief. A night and day difference from their stock form. It is amazing all the power locked up in these saw engines.
Nick