I did it several years, ago, so don't remember exactly how.
I am sure that you will chance upon the solution.
But one partial modification is that for my larger windows, I only replaced one of the two springs. One is enough to keep the lens open. Not all the way up to the ceiling, but enough. A problem I had with two springs is after the last dog was released, but still stuck to the gasket, sometimes, the port would spring open with a lot of snap and give me a good whack across the face!