i use uni thread, and it does not lend itself well to a split loop scenario. I have tried to use some of the twisted fiber threads in order to enable me to use a split loop approach, but always end up fraying the thread and get a big booger when I try to whip finish the fly, so I use the loop approach and do not have a bulky head on the fly ,down to size 20. don't tie anything smaller than a 20 because I cant see it