The biggest problem with hamstring inflexibility during olympic lifting is the way it pulls the pelvis under during squats - this results in reversal of the lumbar curve, which places undue pressure on the ventral surfaces of the vertebrae. Normal spinal curvature also creates the most stable and rigid back, so anything short of that means risk of injury under loading.
You said you're able to air squat to full depth, but is that with a correct lordotic arch in the lower back, or is your lower back rounding at the bottom? In an unloaded squat, you'll likely be able to get away with this without any real problem, but if you introduce a load overhead or on the shoulders, you're placing a large moment on an unstable spine.
Have you had any success with PNF stretching? If you can, rope someone into helping you. Lie on your back with some kind of support for your lower back curve and have your partner push your leg toward your face. Start with just an easy stretch for 20-30 seconds. Then push against your partner's resistance (activate the hamstrings) while they hold your leg in place - do this for 5-6 seconds. After this, relax your hamstrings and have your partner push your leg gently into a little greater of a passive stretch, and hold it for 5-10 seconds. Repeat that process a few times. On the last set, you can activate your quads/hip flexors and get a little reciprocal inhibition working for you.
Make sure you're super warm before stretching like this.
If that doesn't work over time, for a small fee I can graft some extra long cadaver hamstrings into your legs.