I am sorry to read that Linn and Reuben had no chicks this year. I am not familiar with what the site looks like, but am wondering if there is a reason why they have never been given a nest box? The new nest boxes CPF has installed at a couple of sites this year look as if they provide good protection. How can I help with providing one for Linn and Reuben?
I think one of the reasons for no nest box is they never know which ledge Linn will choose. I'm not sure how large the ledge spaces are either.
Each side of the building has 2 small corners with gravel where I have placed the big pink arrow below...that's where she nests

I think she has used a different one several times. There is a small overhang on each one that does offer some protection...she's part way under the overhang in the pic below.

Hopefully just one more part of the very odd year it's been all over.