(M/M) (Weight Gain) (Muscle Growth) (Some Hyper)

Thunderlane has the ultimate Pegasi's build. He is trim, fit, and has abs you could use to grind steel. However, that's not what he wants. Since he was a teen he has been aiming for a true bodybuilder's physique like Big Macintosh's, but has been stuck with the body of an agile flier. Being given a special tome at the Rainbow Fall's Swap Meet will allow him to fulfill his dream of a fuller figure, but not quite the way he was expecting. With a week's vacation time to explore the magic's within, how will he handle being the biggest stallion in Equestria (in more ways than one)?