Multi cat home, cat spraying

Help please! This is going to be a long post, I'm sorry. We have two cats. We got Charlie first. He was two months old when we got him. Charlie is a great cat, super nice and cuddly. Two months ago everything was going so well, that when we came across a 10 year old spayed, declawed female cat (Piper) that needed a home we thought, why not. Big mistake! When we brought Piper home we started off confining her to the spare bedroom. My wife and I would go in there and spend as much time with her as we could but she never seemed to get comfortable around us. We also started chaperoned meetings between the two cats. It started out with a child gate in the bedroom doorway, feeding the cats on either side. Charlie was very curious of Piper. Piper would only growl and hiss at Charlie. Eventually we took the child gate down and positioned ourselves between the two of them. Their attitudes towards each other never really changed. Charlie was super curious about Piper, and Piper freaked out any time Charlie got near. After a week or so we were letting piper out to roam the house while Charlie was confined. And then another week after that we were having them both out. Still their attitudes hadn't changed towards each other. There were frequent fights, Piper was always the one running away and Charlie would give chase. We would often lock Charlie in the basement for a few hours after he attacked Piper. So things were bad. A few weeks whet by like this and then things got even worse. Charlie has started spraying all over the house. So much so that we have to keep him in the basement at all times. I sometimes let him out for supervised visits upstairs but even with me following him around the house he will still spray. I of course scold him send him back to the basement. We just got Charlie neutered this week. We were hoping that would stop the spraying, but no luck. Also 2 weeks ago we got a couple of the feliway diffusers and those haven't helped much. Where Charlie is spraying isn't consistent. He's done a cluster of sprays by the front window. He's sprayed by where Piper likes to sleep. He's sprayed on my leg when I've been sitting down, twice! He's sprayed on the entertainment center, backs of couches, various things in the basement, the list goes on and on. I forgot to mention that when Charlie was upstairs we would try to keep him entertained and even try to tier him out so he would be less apt to go after Piper. But he has a boundless supply of energy and even after getting him to an open mouth panting state using the laser pointer, 10 minutes later he would be tracking her down. I'm out of ideas please help.

All of the hormones may not be out of his system yet. It can take up to a month. I would go back to no contact between them and reintroduce as he adjusts.

We are going to keep them apart for a while. Thanks