Based on chasing the Sandies for the past twenty plus years on Richland Chambers, I'd agree with the couple of comments about "like size" fish schooling together. It's uncanny how often you'll be on a school of good size fish and the bite slows and then all you catch are small Sandies (or Yellow Bass on RC). Might as well raise the TM and move elsewhere. Often times you may only need to move 100' or so and find the school of big fish again.
I've never had much luck dropping a Slab below smaller fish and finding the larger ones. It's usually just more small fish regardless of the size Slab. We do put a 1.5oz. or 2oz. Slab on for the Hybrids but small, medium or large Sandies will all hammer a 1oz. RSR Shad or Minnow Slab. ( www.rsrlures.com
) We've not had much Top Water action the past couple of years on RC so not much recent history on finding bigger fish below smaller Top water fish.
Good Luck and keep playing around with a Slab and you'll figure out what works best in different scenarios!