Kind of neat to see the board from this perspective, as we won't be able to later.
After priming the hole with straight epoxy, the straight end of the tubing was heated with a plumbing torch and doused in water, then cleaned, slathered with epoxy, and inserted in the hole in the trunk log. Using a metal plumb bob (has a nice conical shape), I started a flare and then switched to the ball-peen hammer for the finish. It was quite easy to create the flare with this method - Thanks Peter!
I learned a couple things doing the fillets: one is that I am not convinced that the blue tape was worth the effort. It took a a fair amount of extra time to apply, and then to remove, and I still had to do some cleanup inside the tape on many fillets. I think I will try a few fillets without the aid of tape next time. The second thing is that it would save a lot of time and effort if you can apply the fillets soon after the parts are glued together - the squeeze out from the glue-up becomes part of the fillet, and no prep (sanding, etc) is needed before adding the fillets. This, of course, requires some planning so that you have time to do all of this in one go.
I started by drilling the 3/4" hole with a forstner bit on the outside of the trunk using the portable drill jig screwed to a pieces of plywood clamped to the trunk side.
I then inserted a bushing in this hole, and a 31/64" drill bit in the bushing, and drilled through to the other side of the trunk. I then clamped the plywood fixture to the other side of the trunk using the 31/64" bit to position it, then switched to the 3/4" forstner bit.
The result was that the hole on the inner side of the trunk was a little less than 1mm low for proper alignment with the outer hole. Using a round file, I enlarged the hole a bit to allow the inner bushing to be aligned with the outer bushing.
I installed the centerboard in the trunk several times during this process to check alignment of bushings. When I was happy with bushing locations, I had to insert a sliver of HDP (high density polypropylene) that I had laying around (no, I didnt cut up one of my wifes kitchen cutting boards), under the inner bushing to hold it in alignment.
After a prime of neat epoxy, and ample scoring of bushing surfaces, I glued the bushings in place with thickened epoxy. I started by slathering thickened epoxy on the hole and the bushing, inserted into the hole and put packing tape on the trunk inside side to limit squeeze out on that side. Added the HDP sliver to the inner bushing. Let this setup for 15 min or so, cleaning up squeeze out, then removed the tape and inserted the SS pin (coated with wax to keep from gluing it in) so that the bushings would be in proper alignment while epoxy cured. I checked every 1/2 hour or so, and rotated the pin to make sure it wasn't getting stuck. After about 4.5 hours, I removed the HDP sliver and filled the hole with thickened epoxy using a syringe.