In looking at some photos while putting together hathor.info, some details became more apparant. (I "fipped" and resized some of the available photos to make the composite below.)
The first thing I noticed was the mast on the boat in its "1950" photo. I asked Larry if the mast could have been from the Doreen and he answered:
Good eye, yes it was the Doreen's aft mast. That was why we had to go
foraging for another.
Now I wonder how Larry designed the support of the new aft mast. (There are some steel angle members other places in the canopy, and I think he built a structural box beam of aluminum to support the aft mast on Sea Lark.)
Then there's the stack. It looks like the original was cut down; probably when the boat was remodeled by Garnet McKee in the 30's. Larry replaced the shorter version with one about the same height as the original ("steam engine height") for Hathor's recommissioning.
There is center aft canopy support in the 2011 view. It was a temporary brace (a 2 x 4, removed for the recommissioning ceremony) and its structural function will have to be replaced with a permanent solution of some kind, especially if people are to be tramping around up there. That will be tricky because I think Larry wants to retain the original flag pole support.
Now take a look at the transom on the day Hathor was hauled for its seven-year rebuild. Compare it with the way it looked on the day the V-8 engine was installed.