I'd do a wire to rope splice but for 2 ropes, I'd double the length of the buries. If you have the means, load the splice to couple thousand lbs and see if it works. This isn't common but it might work. Also choose the largest double braid you can use on your cleats. Ropes that are sized similarly, are easier to splice.
The real answer is to use smaller line.
Who wants to coil 1-1/4" line?