If you're getting a big knot using the Imp. clinch, you might want to think about how many turns you're putting into the knot when you tie it.
Prior to making the loop, try only going around the line maybe 4 times or so and also lube your knot well with saliva or whatever so it becomes as compact as possible.
That may take the size down some.
Or you can try another knot like one from the link albatross provided.
I've been using what we always called the Uni-Knot for about the last 25 years. I don't remember if it is in the link above. I'm pretty well satisfied with it. it's a great knot that not only secures a fly pretty well, but can also be used in lieu of a surgeons or blood knot and is also the only knot I bother with to attach a leader butt to a fly line. For this purpose, it's alias is the nailless nail knot.
Very versatile knot. Does everything but make coffee...
http://www.cabelas.com/information/cabelas-field-guides/Knot-Library-Fishing-Knots/Uni-Knot.html