I have a better question.. How do we know if the Hypolimnion is even present???
If it is, why do we want to blow air through it and dump surface heated water into the mix?
Why is it important to have 65 deg water? What is the reason behind that?
No, that doesn't answer the question but there are WAY too many variables to suggest we can achieve "X" temp at "X" depth.
Maybe I missed the target ewest is looking for.