I don't know what percentage of my sets are flats but by far most of them are. I don't know why, but I don't often think of a walk through and coyotes in the same breath; and I know that walk throughs are very good coyote getters...funny how some things stick and others don't, and I use walk throughs for cats! Anyhow, I set my pan 7.5 inches from lure ( the distance from the tip of my pinky to the tip of my thumb, just messured it for this post). I have some sort of natural type backing, grass clump, catus ear or arm, bleached bone, scat, cow pie what ever is handy. I use subtle guides with one most always tight to the lure side jaw and none near the free jaw. I use a variety of traps from a few 1.75s to #3 bridgers and #4 dbl longs and I set them all the same; it works for me.
I'm in complete agreement with Slim Pederson when it comes to foot placement coyotes smell what's at their feet just like dogs. I can't catch coyotes with the traps back at 12 inches unless I'm using some sort of stepdown. Now if you are of the mind to raise the lure up off the ground you will need to get your trap back a bit.