This is not a huge deal on this forum and I don't mean to bust your chops here Bill, but there is a very definite distinction between the "classic" SBC and the LS series. It's about as subtle as the distinction between the flathead Ford and the Y block that followed. Yes the old and new share some similarities, but the new was a groundbreaking, clean sheet design. I only bring this up because I know you are a stickler for correct terms and if you want to communicate properly with a gearhead, the terms "SBC" and "LS" set very different expectations for whatever conversation follows. Apples and oranges. To the more important point: Doesn't the overall length of the Lycoming main bearing (and resulting massive increase in surface area) contribute more to harnessing the gyroscopic precession of the prop than the overall diameter of the shaft? Or are we only concerned with the cantilevered section of the shaft outside the bearing?