So, given all of that there must logically be issues with the crew members weight. Would I be right in thinking that if a pilot is over a certain weight the ejection would not be "clean", also if the pilot was small and light then would that not be a problem too?
The relationships are complex, but yes, pilot weight makes a difference. I'm short statured and was flying an A-4 on a sandblower mission. At 100ft AGL and 400KIAS the power turbine failed catastrophically and I had to eject. The combination of airspeed and my weight and weight distribution made the ESCAPAC seat unstable. Things did not go well. After recovering, USN prohibited me from flying ejection seat aircraft and I flew P-3s for awhile. Later, USN bought a cool new jet called the Hornet which had a new fangled Martin Baker ejection seat. This was the first aircraft USN bought that was designed for pilots ranging from the 95th percentile male to the 40th percentile female (anthropometrically I'm pretty close to a 50th percentile female in most measures). The seat could adjust to compensate for pilot weight and was stable over a wider speed and CG range. So they reassigned me to fly Hornets. I never needed to find out if the Martin Baker seat worked as advertized. But the bottom line is that modern ejection seats have much more capability, including having the ability to steer and alter their trajectories dynamically. They don't just fly in a straight line. I understand that some of the newest Russian seats are especially impressive in that regard.