Hey Walkinpool: we just finished our 6 month stressful build - small relaxation pool- last week - getting ready for pool school tomorrow. Look at this beauty - so relieved and excited! On depth - we never thought about deeper than 5’5” because we had a large 7’ vinyl lined pool for 25 years And I had the same opinion as your wife. I am 5’3 - my husband is 6’4”. Our contract was for a 3.5 - 5.5 - but the end result is actually just shy of 5’ at water level, because I can stand up at the end and the water line is at the middle of my chin. So - I now wish we had gone for 6 1/2 feet in order to clear swim (or walk) at a water depth closer to the high 5’s - if that makes sense. It won’t be exact. My husband contends that with only a 21’ length, the floor would have descended too steeply for comfort and the purpose of our pool is relaxation. So actually - he’s good with it. Me? I have no choice but I encourage you to go for the additional 6”. I think you will both end up with what you want. Hope this helps.