I have a pretty broad (chubby) build, but absolutely love Longwood! The Letterbox squeeze isn't too bad if you take plenty of care to position yourself just so and fully commit (i.e. push off something with your feet and simultaneously exhale/relax your chest). The traverse in main chamber can provoke wobbly legs moments for the less confident and it may take you a couple of goes to find Christmas Crawl?
Overall a cracking trip that provides a bit of a challenge, plenty of pretties, water? what more do you want?!