I have the model D and it took me about a week to master it. If you are not doing it already, try practice in the bathtub, it'll be less frustrating if you make a mess. And try to spread your legs further apart and tilt your hips forward, makes it easier for the urine to flow down. Most of the time, leaking occurs because the urethral opening is not completely covered by the stp funnel and form a seal, and most people don't realize the opening is further back in the crotch. When I first got my model D, I tried to position the funnel as far back as possible without hitting the butt crack, once I have a successful attempt in peeing, I moved the funnel forward a bit until I find the optimal position.