The Hulk can get much bigger than 15 feet tall. The Guilt hulk is around 120 feet tall. Hulk only starts getting bigger when he's severely pissed. His body has to grow to accommodate the massive adrenaline rush. In Hulk's case: adrenaline = dramatic strength increase and gradual growth. The more adrenaline released, the larger and stronger he gets. The larger he is the more adrenaline he can hold, and the stronger he can get. This can continue indefinitely. Thus his strength and size increase can be regarded as infinite.
i like wolverine alot, but in saying that wolverine never actually won any fights against the hulk, it was pretty much a win in hulks favor to me cause wolvie was hurt an hulk was not, it was either guessed that his claws weren't long enought to get all the way through the hulks tough hide like skin to get to any vital organs or that logan didnt possess the strength needed to drive em deep enough either way wolvie woulda had a bad day if the hulk got ahold of him