I'm in the process of doing something similar right now, except growing out HSB and BGxRES in my two grow out ponds. One issue I'm having is having the ponds seal. Largely because they were so small and so steep I couldn't get equipment in to pack them. Next spring I plan to try Soil Floc and if that doesn't work install liners. That may be one thing you need to concern yourself with.

Also, I built mine in a circular shape so that I could use the pressure of my well to circulate water and aerate with 'horizontal' aeration instead of traditional vertical aeration. Essentially I'll be creating a lazy river effect.

One thing TJ told me to is to dig one side with a slope you can drive a skid steer to the bottom of to re-excavate after 2-3 years. This may not be a problem since you are going so deep, but it may be something you want to consider. He thought my ponds may lose 3-6" per year due to fish waste from heavy feeding.

Good luck and share your experience.

Just a Pond Boss 'sponge'