Wow, I don't know how I missed the box in the top left with the hour increments for GHA. I think I started ignoring that box because I thought I didn't need it. Anyways, I did another calculation somewhere near Aberdeen and got a 3 arc minute error in latitude compared to what the navigator said, as expected.
Now if I could get sophisticated enough to determine the ever elusive longitude.
And yes, it has been years since I've played SH5. Computers in the year 2021
might be powerful enough to run SH5