faugh a ballagh
clear the way irish brigade!

I thought they were good for Danish 1864 at first glance but the jackets need to be double breasted.

I notice these Danes carry their rifles (at slope) on their left shoulder and I thought this was fairly standard and still is. Not sure why but it leaves the right hand free to pick your nose. The slope arms are a bit vertical on the models and look from the pics as if they are balancing them. As I write I bet somebody is sifting through all those surviving ACW cartes visite to prove that they have blue tunics that are not too short nor too long. Most of them got their mums to take them up or let them down before a photo but generally there must have been a lot of variation. I mention mums because with their whiskers and sideburns this batch look skewed to the middle aged gent type who could handle fancy needlework themselves.

The US Army did not use "slope arms", period. Shoulder arms was the norm, with the right hand wrapped around the trigger guard and the rifle carried vertically, tucked in to the right shoulder, as per Hardee's Manual.
https://usercontent2.hubstatic.com/8660657_f520.jpg

Some Virginia units in the CS Army used Gilham's manual where the rifle is carried sloped back over the left shoulder, left hand gripping the butt as in these figures.

The other most common position used for movement at the double quick, was "right shoulder shift": the rifle is held with the right hand under the butt and angled to the rear and left, behind the soldier's head

http://acws.co.uk/gilhams/images/gilh013.gif