In project management point of view, missing target is unacceptable. In this case, the change request (with strong reason) should be raise before getting to the dead line. However, this is the lesson learn for all of you to aware of it and this should not happen again. Development took a long time than initial estimate. Moreover this is the 3rd solution that we found it is the best solution and of cause we can't release with 1st/2nd solution. Team did a lot of performance testing (this is time consuming) to ensure the performance is improved.
The dead-line of this e-load is changed to 15/08/2013. I do not expect this will miss again.