Lol I just finished reading the whole thing.
Pretty interesting, definitely kept me entertained. I once had an idea for a fic that was kind of similar, involving a seventh Animorph (like David) using the morphing ability for their own personal gain, but only sexually. Even though there's a lot of dirty fanfiction involve the canonical (and non-canonical) pairings, I feel that the idea of using morphing specifically as a sexual tool is a fanfiction market that, much unlike Ax's ass, remains largely untapped.