Long ago some1 told me the golden rule of dogs.:................. They live SOLELY to please you. It is SOLELY up to you to teach them what pleases you.
While Akitas for show need to be close to standard size, as long as the pup is healthy and developing correctly, I really wouldnt worry. Barring sickness or injury, he will be what his genes determine him to be.
And as I have stated many times, what makes an Akita is PERSONALITY and ATTITUDE. Size, shape, coat length, color mean nothing except for personal preference. Health is everything.