A weird inconsistency in the Aru Shah series is, in the second book, when Mini, Aru, and Aiden were running from the cows, Vajra in hoverboard form could fit all three of them. However, in the last book, during the final battle, when Vajra was at its most powerful, it couldn't hold two people: Aru and her mom. I've wondered if it was because Aru's mom was an adult and maybe Aru had grown, but it's still only two people compared to three people in the second book.