Digga and I have been doing a lot of riding lately.
Big and Small: 1UP USA rack will fit a fat bike and a 20" wheeled bikes. It is a great investment. If you are looking for a rack, stop and get one. They have a roof mount option as well.
There is finally some green. Digga rides like a champ. There are some challenges and occasionally he has to walk his bike but what mountain biker hasn't.
He has an amazing amount of energy. He found a gear that worked in all situations. He may spin out on the flats, but he is a motor.
They have closed the bridge to Sylvan Island so we spend a lot more time at Sunderbruch Park. The green rated trails provide a little challenge but do not overwhelm him.