Yes, 7.5 inches is very tight. In my past experiences travelling with our King Charles in a standard 9 inch carrier I have been given a window seat which allowed me to keep the kennel along the wall lengthwise which gave me some legroom during flight. Some FA are ok with this since it is not an obstruction in case of emergency while others are very insistent they must be in the footwell especially during take-off and landing.
Soft cases work best as you can make them conform to the space during this time then moved once airborne. Hope this helps