So I thought I'd go back and check a calculation I did a few months ago--I'd use the same procedure, and just confirm that the results made sense.
Before: 25% of the 27Si created decayed to the ground state of 26Al, and 25% to the first excited state. A total of 50% of the 27Si was accounted for; 50% was missing and I wasn't sure whether it was an efficiency problem or just something weird I was doing in the analysis.
After: 75% of the 27Si created decayed to the ground state of 26Al, and 75% to the first excited state, for a total of 150%.
Not, perhaps, the subtle change I was hoping for.
Excuse me for a minute. I think there's a wall that needs me to bash my head against it.
(Edit: just after I finished writing this, someone came home with a whole bouquet of free-range flowers for me. All better.)