Learn SCASM I'm affraid. It's because of the age and type of the model, FSDSV1 or similar program, which causes this type of problem. No amount of tweaking airfiles or cfg's will help, it's all the model.
If you learned SCASM it's possible to convert it to FSDS2'ish standards and eliminate such problems. Only a very few people have successfully undertaken such endevours and succeeded. It would be easier to learn FSDS2 and build a new one from scratch, SERIOUSLY!!
best of luck,
Jamie