I assume when you say under stocking, you are referring to a much lower number than suggested?
This is my experience on understocking a 5 acre pond.
First off we Rotenoned it in May ‘23 and started out fresh.
Once the Rotenone was non toxic (7 days) we stocked 85# of FHM. They had sufficient breed grounds and the reproduction was crazy
In September ‘23 we stocked both LMB 2” and BG at the same time 100/1000.
By June ‘24 we had catchable fish, At the 1 year mark we had LMB in the 14-15” range
By September’25 (2 years) we have caught LMB in the 4# - 18” range and BG over 10” - 1.4#
Now the catch rates of the LMB are pretty slow but their size more than makes up for it.
We are also already seeing YOY LMB over 12” and BG reproduction is insanely high.
Up til now IMO structure and a little supplemental feeding are the keys to success.
With that, I weigh and measure every fish, anything under 110% RW gets culled (8 so far)
I also fish the pond 5+ days a week as long as the weather allows and it has not slowed the bite down at all
We also added 50 CC and have caught a few over 6#
There are a bunch of “you did this wrong “ and “you should have done this differently” in my approach but up until now I believe the results have spoken for themself