I think it really depends on your lifestyle and your comfort level. 7.5m to 8.5 is a big difference for alot of people. What are your concerns about a 3ct ring? Too big for your finger size, believability,etc?
Not my finger at all, believability would be one. When I decided I was sick of my old ring looking like crap, my main objective was to find something that everyone would believe was a real diamond. I saw the reactions when people looked at my ring; first a smile at the setting and oooooh so pretty and then the realization of the center stone....it was blech. Embarrassing to say the least.
I wonder if there is nothing he can do...I am open to modifying the ring a little in order to allow a smaller stone in the middle.