In the past I've had great results by doing short range of motion abdominal movements (outlined below). I started doing them in this manner after noticing that I was getting a lot of undo body movement (swing) and would fail on hip-flexor exhaustion rather than abdominal exhaustion.

My question is, are there any drawbacks to limiting the range in these exercises? I'd like to do more full range movements, but find that other full range movements over emphasize hip flexors, and add lower back into the mix.
Is it common to pre-exhaust abdominals before doing full range movements?

Exercise 1: Hanging Leg Raises
Starting with knees at 90 degree angle to body, I raise them as high as possible for a 2-3 count, then lower them to 90 degree position.
Sometimes I drop the count at the top and add weights between my feet.

Exercise 2: Decline Bench Crunches
I start sitting on a decline bench while holding a 25 or 35lb weight.
My beginning position is leaning back at a 45-60 degree angle to my thighs and then coming forward, exhaling and concentrating on flexing my abdominals until I'm at roughly a 60 degree angle (in relation to my thighs) leaning forward. The weight in this motion isn't used as resistance to the forward movement, rather to provide assistance in the muscle contraction.

This might sound crazy if you haven't tried it, but it provides an excellent contraction that I find impossible to duplicate with other exercises.

After reading Nick's article on plank exercises I intend to incorporate them into my ab workouts as well.

Other full range exercises I rotate into my ab workouts:
Flat bench leg lifts
Bicycle crunches
Cross bench crunches