great questions baltic pit, and welcome to PB.

seems to me the depth needed to avoid excessive aquatic veg. will depend ultimately on the average water clarity of the pond. what is the average clarity of managed or unmanaged ponds around you?

for my 1 acre pond (which is not really applicable to you), weeds grew as deep as 10 feet prior to when i started aerating. after starting aeration, the water column was able to grow more microorganisms and maintained phyto bloom longer which reduced sunlight penetration and weeds mainly took hold in 3-4 feet water or less.

i would make sure mounds are well compacted and 2 feet sounds a bit shallow for the types of sustained winds you get in SD. just guessing here but you may find erosive action to extend that deep, and you probably want your mounds at 4 to 5 feet down. mounds at 2 feet will also grow alot of weeds....but again, just a SWAG.....maybe others will chime in on this.

sounds like a great place.

GSF are people too!