All the comments about F15 - F40 being a lurch are correct. F25 smooths it out and is not necessary if landing F30. For irritations here's another. Guys landing F40 call F15-F30-F40. Why are they afraid of F25? Plus there is no bug for F30 if Vref40 in use, but there is a F25 bug. Why call a flap setting for which there is no bug? I know Vfly F40 is OK for F30 in transit, but it's the philosophy of calling a flap with no bug and not calling for a setting where there is a bug. KISS