I have now installed the mast trunk, which I assembled outside the boat some time ago. This part had a bit of twist to it and I was a little worried about being able to get it installed straight, but having the surrounding pieces firmly fixed helped a lot, and I was able to get this nicely aligned using only a couple handscrew clamps. The lower portion was fixed in place over the keel and in slots in the bottom hull, and applying the clamps twisted the top portion straight against bulkhead 3.
After installing with silica-thickened epoxy I followed up with fillet mixture. I was glad to be done with the fillets back in the narrow hard-to-get areas.
Here's a view down from the top. I'll have to reach in through the front of the box to try to get a fillet on those corners (to the right in this photo).
This was a good job done. Nice to get the 'engine room' in place.