Turn it to 22 and let it idle, prove it to yourself, if it changes, recurve the distributor to the same total.
You have too many cooks in the kitchen. I have to be honest, the same questions over and over hoping for a different answer is real frustrating for old heads.
I PROMISE its not WAY TOO LOW, but if you recurve, play with 22, just remember it may not like to start hot and you may have to slow the curve down
I have to tell you and I am going to say it in a way that sounds like a dick. LOL
You don't even know that you HAVE an overheating problem, you keep starting the car and letting it idle with uncoated headers and repeated changes under the hood, but you are so hyper focused on it, we can't get past it.
Try it, let it idle, and like I said yesterday, let it idle and get real hot, see what it does, at 15 or 22.
FWIW, even the slightest movement will wick air away from under the car too which will let the fans work better.
If you think those guys know more than the guys here, use them, but watch out, Jay knows where timing should be based on that chamber design and quench, we all know what runs well on the street, and using the generic answers has melted a lot of pistons over the years