IMO a small 0.25ac Indiana pond would be much better long term if it had 8ft-10ft or 12 ft depth. Once dug it would not take very much extra time and $$ to dig the small belly area 3-4ft deeper than 6ft-8ft because the bottom of the funnel shape area is a small square footage..
Instead of using regular HBG (BGXGSF) seriously consider using specklebelly HBG (BGXRES) SBS. I think this hybrid will grow bigger than the regular standard HBG. Another bonus to SBS will be the surviving offspring genetics will not revert toward the green sunfish genetics. There are a few places in IN where you would be able to get SBS. Jones Fish Hatchery and Shelby Fish Farm in western central OH. Steve at Shelby is raising some SBS overwinter inside aquaculture. He said they are growing fast and by Apr-May they should 6"-7".long. It is common with lots of food for the SBS to grow to 3 pounds. Once state record is 6 lbs for SBS.
Malones' suggests 25 to 50 SBS in 0.25 ac.
https://www.jmmaloneandson.com/specklebelly-bream-.html
