I'll be damned if I can get this to fit on my FLHTCUSE4 - if I push hard enough to get the tabs down between fairing and windshield, then the two end bags are so distorted, they're unusable. The down turn of the two end bags is just too close together to fit the dash. Maybe I'm just mechanically challenged, but have tried everything I know (including leaving the bags out in hot sun to "loosen" them up)
Don't give up. Loosen the 3 front screws as far as you can without unscrewing them. Then loosen the upper inside fairing screw as far as they can go without unscrewing them all the way. Then maneuver the bag to just get the tab started between the inner fairing and windshield.
Once you get it started, then push down on one bag at a time until the lower sewing threads of the bags are all the way down to the level of the inside fairing when viewed through the windshield. At the same time as you are pressing each bag down, tighten the front fairing screw opposite the bag with your free hand so that its just tight enough where the bag doesn't try to rise up when you move to the next bag.
Then move to the next bag and do the same thing. Once you're done with the 3rd bag, go back and tighten all three outer fairing screws and then the 2 upper inner fairing screws. You're now set. Its worth noting the 2 outer bags are not very big to start with. Even if they aren't installed on the bike you can only fit realtively small items like a small flashlight, gum, chapstick etc. I found that sunglasses in a pouch simply won't fit in the outer bags.
The next time you need to remove the bag, it will be perfectly formed to the fairing and windshield and you'll only need to slightly loosen each of the 3 outer fairing screws in order to remove the bags. You'll also be able to literally just drop the bag back into place and tighten the screws.
You'll find that after a heavy "rain" ride, it's very convenient to remove the bags in order to clean the inside of the widnshield behind the bags. I've done it many times and its remarkable how easy it is to reinstall the bags, particularly when compared to how difficult it was the first time to install.