I had a little breakthrough on Orbit 13. I managed to get the total weight down even further and got the max speed up to 2382ms, just 23ms less than the recorded top speed of Orbit 14. Apparently those 23 ms makes all the difference because i wasn\'t able to get Orbit 13 to a orbit with periapsis higher than 15km. I have attached the craft files for Orbit 14 and 15.