Would u weigh less during a full moon?

I'm not convinced if gravitational fields cancel each other out...

Sure they do. They're vector fields and so cancel.
Another way to think of it is that gravity is basically a force, and forces certainly cancel - so why wouldn't gravity:

fake edit: source - http://sci.tech-archive.net/Archive/sci.physics.relativity/2006-10/msg01491.html

I understand that, I'm just considering it from curving space point of view. I understand how the force above you will detract from the force below you, producing a different resultant, but somehow I doubt it's that simple with gravity. I would be as though you're being acted on by two separate forces rather than one resultant. You wouldn't be lighter, you'd be pulled apart.

Granted this doesn't explain Lagrange points, so I guess it is that simple

But your "weight" is just the amount of force pulling you towards Earth. If there is a force pulling you in the opposite direction, producing a different resultant (as you say in your post) then surely that's equal to less weight.

Anyway! Some of the stuff you talk about (curving space and whatnot) is way above my understanding. Where / what year do you study at?

Surely it'd be at new moon, when the sun and moon are aligned? (leaving out issues of order of magnitude compared to other effects like latitude.)

A minor point but a new moon is when the Earth casts a shadow on to the moon, i.e. its between the sun and moon.

For maximum pull away from the Earth's surface you'd be needing a solar eclipse, i.e. both the sun and moon pulling you in the same direction, creating a bigger pull instead of working against each other at new moon.

A minor point but a new moon is when the Earth casts a shadow on to the moon, i.e. its between the sun and moon.

For maximum pull away from the Earth's surface you'd be needing a solar eclipse, i.e. both the sun and moon pulling you in the same direction, creating a bigger pull instead of working against each other at new moon.