As the main flow is almost upon me (and my bees) I'm considering doing a cut-down split this year. All I have ever heard is that the timing is critical and must be done shortly before the main nectar flow.
The undefined and purely qualitative term "shortly" is what bothers me and I seek a quantitative answer.
1 week before the main flow?
As I'm dealing with blackberries as the main flow around here and it lasts 3 weeks on average and up to a month on a good year, so do I use the middle of the predicted range as the date to calculate back from?
Based on my bloom log I'd put us between 1 and 2 weeks from the full bloom stage (depending on the weather).
p.s. I did this sort of split purely on accident last year and it was stupid successful (interp as LOTS of honey), unfortunately I didn't record my split date to go with the bloom log notes.