I almost never use Elk hair for the caddis, it’s tough to find good elk that will work. If you look at hair anything above where the tips start to darken it is not hollow so won't float. This area in Elk tends to be rather long and not suitable for small Elk hairs unless you can find yearling Elk.
I always use short fine deer hair. Commercially if you look for X caddis hair or Comparadon hair it works great. On a deer, the ideal stuff is from the center of the back from neck to rump or sometimes leg hair. I’ve also used polypropylene for the wings with good success. On really small sizes #18 to #20 I’ll often omit the hackle.
