I have looked at the tail and saddles on hundreds of Leghorns.It does make a difference on the American type ,backline,and style.It also plays a part on balance and symmetry.I find you do not want a high shoulder,you want cushion or saddle feathers to fill in and build up the back area before the lesser tail coverts,lesser sickles,sickles and main tail.This prevents the break angle at the front of the tail.You need a high tail angle to support the tail weight,the top sickle feathers should be in line with the earlobe. The low tail will prevent the curved backline and will increase the chance of an angle or break at tail.A short tailed Leghorn just does not look right and those with narrow stringy feathers look rough and out of condition.Feather width helps with bloom and condition ,or eye appeal. Feathers take time to grow,especially tail and sickle feathers (about 3-4 months)They seem to grow a bit faster in cold weather.Feathers are fiber and protein,so make sure the diet is good. I like them to get some animal protein regularly(Dog food,beef scraps,beef fat/tallow,mealworms,etc.).Growing or green feathers contain a blood supply and can be a source of feather picking,it is less of a problem with females getting picked.There are many ways to deal with it.Separating the sexes during the brooding and into maturity helps.Free range or lots of space helps.Individual cageing of the promising young males always works. If the tails are fully grown on the males and they are out of blood feather,they can be put into breeding pens while fertile eggs are wanted.For chicks make sure the light is not too strong,lower wattage,and bug lights (yellow bulbs),and that the heat is not too much(use a thermometer).Some people say red lights work,some say it causes eye blindness,so I am not sure on that one.Leghorns are active and need space and exercise,high roosts to fly helps wings develope,free range provides bugs,fresh air,entertainment,and hiding places they can escape(weeds,brush,bushes,trees) from getting picked.Dan Honour