It took more than a month to hand craft this one-of-a-kind Harry Potter replica Quidditch Trunk. Many metal and plastic printed) parts that had to be designed or hand crafted to complete the Christmas present for my daughter Krista.
But, actually, he chose a stag because it was large, powerful, and fast. It could survive a werewolf attack (assuming the worst case scenario happened). When the Marauders told Remus they were animagi.