George, I am sitting here waiting to go out and shovel 3 feet of snow in New Hampshire!  Anyway, regarding the tabbing the bulkheads below the interior deck levels, I would still consider some type of interface between the bulkhead and the hull.

Because of the proximity to the bilge, I would look to use a material other than a kerfed piece of plywood.  On other boat building projects, I had used a pliable foam material such as airex or the like.  This would allow the foam to be encapsulated in glass and to be relatively impervious to water intrusion.  These strips need to have beveling on the side, but the top surface should be the same width as the thickness of the bulkhead:  3/4" for a 3/4' bulkhead.  This encapsulated base protects the hull, as well as provides a very nice beveled surface across which to spread the load on the tabbing.  If done well, the encapsulated base eliminates the need for any additional filleting for a smooth tab.

Our floor bulkheads were tabbed directly to the hull at the factory, and they have survived very well over the 35+ years the boat has been alive.  The solid glass hull is thick enough to accommodate the load.  The method used by the factory is certainly OK, but the method I mentioned above takes the process up to another level.  That upper level could be considered over-kill, but you will have to prepare some very smooth fillets to ensure the strength of the tabbing bonds. 

It may boil down to what is an easier method for installing the bulkheads in your situation.  You know, how much access do you have to make the encapsulated bases or to prepare the fillets.  Do you have access to a foam product to make the base out of?  Etc.

On the Yanmar, I had similar questions for the engine rep and the distributor regarding optimum loading and glazing, etc.  I was told that even though the WS42 is a heavy displacement vessel, I would be OK and that there was no risk.  I still have to figure out the prop question.  We have a large 3 blade prop now, but I am sure it was tuned to the Perkins 4-108 that was originally on the boat.  I have to address that once Spring rolls around.

Now, one thing I was very pleased about with the 110 hp Yanmar, is that the distributor though I had a good chance to get our WS42, Harmony, up on plane with that size of engine.  Boy, I can't wait to do a little wake boarding once we're in the water.  Heck, I might be able to save on bottom paint if the boat lifts that much out of the water!

Kidding of course!  But imagine the possibilities!!!

Doug