Try using GSlide.
1. Download GSlide (Downloads - Softwares - GSlide15 - Top Sony Forums).
2. Extract it and run it.
3.In Flashfile choose your MAIN file.
4. In Output choose where to save a patched MAIN file ( Let's save it on desktop and name it k750_main).
5. Now click Add.
6. Open your .vkp patch.
7.Click Process.
8.Now start XS++ and flash your phone's MAIN firmware with k750_main.