He has definition in his hind, so that's a good start. Can you feel ribs easily?
My dogs are unconditioned atm, but slim. I like to see at least 3-4 ribs on Harlow and some spine. Rider and other ACD's (and Finn too if he's got a decent double coat) I like to be able to easily feel ribs and mayyybe some spine.
Others probably have better input than me.