I'm afraid it's not that easy ... I dropped around 100 GBUs today, trying multiple parameters and methodoly changes and I see a clear and repeatable gap on the very most of them.
I dropped them all by the book, as regards the procedure, of course. Speed and altitude are not the most influencal factors. The AUTO mode is broken somehow, and drops the bomb up to 10 seconds late.
Diving (not ideal) or switching to MAN to drop it in advance makes it impacting all time. But a stabilized flight at a locked altitude with AUTO generates more frustation that impacts on target :)
There are too many people missing their targets to be just a procedure misreading ... I discussed that today with several other people, they all suffer from this issue.