Yolk, are you saying it takes about a 3# or more SMB to eat a 4" BG?
No, I'm not exactly sure how big a smallie would have to be to take a 4" BG, just that as the BG get larger, the SMB seem much more cautious-and that in my pond, that seems to start at about 4". Less than that, game's on, and the BG are voraciously preyed upon.
I haven't experimented with exactly how large a BG they'll take, but probably should.
The smallies Jwwann is putting in should be perfect for BG the size he's showing.....