Persuading an Instructor to replace Midterm % with Final if Final better...

This is an introductory organic chemistry course.

The following circumstances apply:
(1) Method of Evaluation:
1. Online assignments: 5%
2. Lab: 25%
3. Midterm Exam: 25%
4: Final Exam: 45%

(2) Midterm exam is already done.
(3) Final exam is cumulative.
(4) Midterm exam 1.5 hours long, Final exam 3 hours long.

I want to persuade the instructor to use the following policy:
If your mark on the final exam is greater than your mark on the midterm exam, then the mid-term mark will be discarded and final exam mark will count in its place (ie. final exam 70%, midterm 0% if you do better on final).

I would appreciate any input.