标题写出重点就行了,是我的话,我会写：a little more time
你的email写的挺好的了,稍改一下：
Thank you very much for your work for ACTA-A-08-0108.I am afraid that I will not be able to submit my revised manuscript on time.According to the comments,further experiments are needed by rotating disc electrode (RDE).Up to now,the experiment is in process and the results are satisfactory.But,more time is needed to complete all the experiments and perfect the paper.I wish you could understand my delay.I'll try my best to submit the manuscript by xxx (填上一个固定的日期,以示诚意）
Sorry for any inconvenience caused and thank you again.