I had something of a "eureka" moment the other day - it occurred to me that my little batching technique used in the previous version of the code was essentially duplicating what the CL runtime does anyway (and better), the key is simply to use the group size for the same purpose. So I eliminated those loops I had before, elimated the `buf[2 * 4]` local storage, and switched to using a (2, 4) local size and a single `buf` register in the kernel. Got exactly the same performance from a much simpler kernel (yay, learned something!)