Since I'm commenting on this thread, let me suggest the reason Randy has cautioned us about properly seating the front bearing lest we ruin it when we tighten the prop is due to Brinelling.
The engine should be set up by the manufacturer to create proper axial fits using close tolerancing of all of the pieces: Case (shoulder to shoulder); crank (web fillet to front bearing seat); main bearing (width as measured across the two races in preloaded condition); and, the front bearing (width s measured in preloaded condition).
The bearings in your engine are back-to-back or "DB" preloaded. This tells you the contact angle direction. This orientation is used for higher moment stiffness (can handle the pounding of the rod better without the crank tipping in the bore) but it does not like misalignment. If you change the internal clearance of the bearing, because all of the other geometry we've mentioned here is fixed (ie. machined in), you've changed the preload. A lot of factors here are interrelated.
If you fail to fully seat the bearings, then cranking down tight on the prop nut will cause a large axial load to be transmitted thru the balls while things try to draw up. There are fewer balls (and sometimes smaller balls) in the front bearing, and it also has a smaller radius of curvature, so you will damage it first. This is called Brinelling. You are causing surface damage (and subsurface damage) to the balls. Making flat spots in the balls, in colloquial terminology. Nothing says in aggressive instances that the main bearing won't be damaged as well.
Perhaps the most common reason that a bearing is not fully seated is that the case was not hot enough prior to installation. A secondary reason might be that a proper tool that pressed only on the outer race was not used and the installer "was trying to be careful." But the worst is if the race gets cocked in the bore due to an improper setup, potentially galling the bore, creating a burr, etc. I have seen this with bearings installed using a hand-held tool and hammer. It could also happen if your press has a crooked armature or if your daisy wheel isn't seated. This later situation almost guarantees bearing damage unless you are suspicious enough about the feel after it all cools off to take it back apart before wrenching on the crank. In general when properly heated, the bearing should drop all the way to the shoulder without the need for hammers, presses, etc. If they don't, realize that you are on that slippery slope towards eventual damage.
I might also note that in some instances the preload is modified by the tuner when either the parts are non-standard (bearings) or something about the parts is not dimensionally correct. I bought one speed engine that was like this. Since I don't have the drawings, and many of the parts had been "reworked," it would only be an educated guess why it needed bearing shims to get the axial play back to a reasonable amount.
Hopefully I have not misinterpreted Randy's comment. In any event, any errors in the above description are my own....
Dave