[flybouy]

My guess, if it was a "great mod" someone like Cammco would be producing and selling them. The A/C manufacturers design what they build with many factors determining the final outcome. They designed and built that cover with airflow in mind AND impact resistance, vibration resistance, hail and snow, etc. While it's possible to improve one aspect you may be compromising another.

If you want to prolong the life of the unit keep the coils clean and don't run in and out of the door every 2 min when it's 95 deg with 90% humidity.