i'm thinking of putting together a hanger 9 pulse XT 40

i've seen one where the 2 stroke engine was mounted 90 degrees so exhaust exits under fuse and it looked alot cleaner. i was told by LHS that if i did that it would change the thrust angle and could cause problems. i have no idea about thrust angles and wonder why they are so important?

the only reason i want to have it at 90 degrees is for looks, but i'd rather have a good flying model.