Remember Flexwatt does not have a very large effect on the ambient temps. You might find the 75-77º is a touch cool on the cool end and ambient air temps you may find that to get 79-80º cool and ambient that a higher room temps maybe needed.

My rack is in a roo that is 68º or cooler and I use warm side and cool side heaters, upper and lower, warm and cool T-stats (herpstat 4) to hold the correct surface temps with very carefully thought out air circulation so it heats before it enters the tubs (ambients are 79º).