If my locker is 46" deep & full a bag would be 50"...since it's a soft bag, if I just don't fill it to absolute capacity, this isn't a problem in my mind. Am I thinking correctly?
Not a problem. You just need to watch when filling up as your hatches will start to pop-up.
And make sure there is nothing sharp around the fiberglass areas back there.
The bag will conform to the area its filling up.