Ok experienced tiers, I need some clarification about the wing on the Elk Hair Caddis.

I am getting ready to tie some up for my standard box in 12 - 20 and before I start I am wondering why the recipes call for the wing to be about hook shank length, when on the real thing the wing is actually about 2x the body length. Is the length because "it has always been done that way" or is the some rational reason for the imitation to have wings much some much shorter than the natural?

Maybe I should just tie some short wing and some long wing and see which works best.