My daughter is 4, she is 44 inches tall. We are going next week and plan on riding the following: ET, Woody, Transformers, Simpsons, DM, MIB, Gringotts, Hippogriff, Cat In Hat, Spiderman, JP river adv, Ripsaw falls. This is plenty and well worth the trip. 40 inches tall makes it a little tougher decision. Still worth it but would only do 2 days max and then go to Disney.
There are 9 attractions at Universal Studios Florida with height requirements:
Height Requirements at Universal Studios Florida
ATTRACTION HEIGHT REQUIREMENT
E.T. Adventure 34"
Woody Woodpecker's Nuthouse Coaster 36"
Transformers: The Ride-3D 40"
The Simpsons Ride 40"
Despicable Me: Minion Mayhem 40"
MEN IN BLACK Alien Attack 42"
Harry Potter and the Escape from Gringotts 42"
Revenge of the Mummy 48"
Hollywood Rip Ride Rockit 51"
There are 12 attractions at Islands of Adventure with height requirements:
Height Requirements at Islands of Adventure
ATTRACTION HEIGHT REQUIREMENT
Flight of the Hippogriff 36"
The Cat in the Hat 36"
Pteranodon Flyers 36"
The Amazing Adventures of Spider-Man 40"
The High in the Sky Seuss Trolley Train Ride! 40"
Jurassic Park River Adventure 42"
Popeye & Bluto's Bilge-Rat Barges 42"
Dudley Do-Right's Ripsaw Falls 44"
Harry Potter and the Forbidden Journey 48"
Doctor Doom's Fearfall 52"
Dragon Challenge 54"
The Incredible Hulk Coaster 54"