David, I would think you could live with your 7-8 ft and shallower areas in your cooler climate. You are close to .7 acre and as long as you keep with warm water fish and dont over load it I would consider using what I have. Also do a muck depth check and realize that when you aerate properly you will gain some additional depth with the aerobic bacteria consuming the bottom organic sediments (not to be confused with soil that may have washed in over the years)Very feasible to loose 3-4 inches per year of organic muck. This may gain you some depth over time.It would be nice to drain and redo or raise the bank as mentioned but when these are not options just look at what you have in a different light. Good Luck