The suggestion that the midship cleat needs to be in front of the mast is incorrect.
The midship cleat should be at the widest portion of your boat. Indeed, it could well be a bit aft of that point.
My cleat is at the forward end of my inboard jib fairlead track, which is well behind the mast, and close to and a little aft of the widest point of my boat. I have been using it successfully for 25 years.
Here's a little experiment you can do, if you don't believe me. I got this idea when i had my C25 from 1987 to 1998 (when I bought this larger boat): forget about the midship location for a moment and use your jibsheet winch as a point for the springline. Loop a dock line over the winch, connect it to the stern-most cleat on your dock, and power slowly forward on it. You will find that it works. Further, loop a line through your jib fairlead car, move it as far forward as you can, and try this exercise with that. It, too will work.
Just find a good spot where you have, as you say you do, good access below.