I have taken all the bus windows out and put new skin over the old holes. Now I want to put 4 or 5 RV windows in. Has anyone does this that can give me advice? How do you cut the skin to put them in? What do you use to prevent any leaks. Do you cut from the inside first or the outside? Do you drill the corners first then cut? What do you cut with? How to you frame the windows to keep support in the bus? Any help is greatly appreciated? Thank you in advance.