I designed a rocket and put it into Rocksim, I'm using the F35W-5 motor for this rocket. It is 31.5in with a 3 in diameter and weighs 665g fully loaded with the motor and the payload. When I let Rocksim calculate the Cd it simulates the rocket going 887.25ft. However, when I actually launched the rocket it went 652ft so I adjusted the Cd and found that the Cd would be .56 if it were to go that high. So I tried removing 8in of the body tube in Rocksim leaving the same Cd .56. Now it weighs 603.32g fully loaded ready for launch and it still wont break 750ft in the simulation. It averages an altitude of 740ft. I'm not ready to cut 8 inches off of my rocket that I've been working on for months not knowing if it will reach the altitude I'm trying to achieve. Any advice would help with reaching the proper altitude or let me know if I'm doing something wrong or I need to change something. It would be greatly appreciated.