If you guys are relying upon Wiki for the 7 or 9 kills, I would not trust it. The Wiki post also states this...
"The Komet was equipped with two 30 mm MK 108 cannons which had a relatively low muzzle velocity, with the characteristic ballistic drop of such a weapon, which meant they were only accurate at short distance, and that it was almost impossible to hit a slow-moving bomber when the Komet was traveling very fast (four or five hits were typically needed to take down a B-17)."
The bold text has no basis in fact nor reality. Perhaps Erich can weigh in here, but I would suspect that those 30mm hits/B-17 kill numbers are VERY conservative. I suspect in reality the Mk 108 cannon was much more effective.