As far as I can see he looks great to me - and if the vet was happy then thats what to go on - more often than not round here they are telling people their dogs are too fat

How I had it explained that works for me
Make a loose fist
Your fingers should feel like what his ribs should feel like (if that makes sense) and the spine like what your knuckles feel like when your hand is flat

Looks fine to me, but the best person to give you advice is Mahooli on here, as she has poodles,