Two suggestions that may help you make it smaller.
1. The last subtraction doesn't actually do anything. It takes a random input of 0-15 and produces an output of 0-15.
2. Comparators have the property that if they are measuring the fullness of a container through a powered block, they only output the fullness of the container, not the signal strength of the block — unless the block is at signal strength 15. Take the first hopper (the one closest to the initial torch) and fill it to signal strength 7. Now replace its piston with a block with a torch on top under a block between the hopper and comparator. Replace the initial torch and comparator with a block so that the 7-hopper is now the originating signal for the whole line. Now that slice chooses whether the initial signal strength is 7 or 15, without needing the initial torch sticking off the side.