Regarding the use of variables to be more code efficient, I don't think variables are more or less resource intensive. They just can save you time adjusting values later. However, specifically using the FML function to call a formula into another formula is definitely more resource intensive and should probably only been done when necessary (Not enough lines of code to write the whole formula again, etc). Regarding the "stair-stepping" pattern you see after adjusting the X-Axis, are you still using version 9.0? If so I believe this should be resolved by upgrading to 9.1.