I'll take a scientific study over the subjective observations of an individual any day, and additionally, my subjective observations suggest to me that decline bench is unnecessary for lower chest size.
Lower and inner chest development are dependant on 2 things, the shape of your pectorals (genetics) and the overall size of your pectorals (diet and training). Bench angle is irrelevant.
Now would someone else find the peer-reviewed evidence for this please. I know its exists, I've read it. I'm just too lazy to look right now.