Good looking dog, but a bit overweight! It's so much better for a young dog to be lean, for their joints both now and later. IMHO what you want to see is a pronounced taper after the rib cage before the hips/hind quarters, a good tuck in their waist, and at least the first 2-3 ribs visible from the side. My puppy continued to grow in height until about 10 months, but they vary a lot. But I'd guess at 6 months he's got more growing to do!
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain