Hi, Jerry -
I am indeed still active on the forum and I think you will be happy with the results if you give them a try. Since my first rbew of this beer, I've got to thinking that about 1 pound of fruit per gallon is about right, so if you brew 5-gallon batches, it looks as if you're going to be good to go.
Up here, the chokecherries are generally "ready" at the end of August/beginning of September, depending on where you are; when fully ripe, they lose much of their astringency and gain a good amount of sweetness. There are different ways to do it, and ultimately I am not sure if it makes much difference. Some add them whole and others steep/gently crush them first (not the pits, just the fruit!) with just enough water to loosen them up, which seems to me like the way to go. There are different ways to do it, but what I would do is add the chokecherries right at the end of the boil, either at knock-out or perhaps with a minute left in the boil. Some add them in a secondary, which I haven't tried. One thing that I read about (and will probably try next time) is to mash them up a bit (gently, so as not to break the pits) and then add them to an empty fermenter. Attach an airlock and let them sit for a week, then dump your wort on them after the boil.
Lots of options!
Another incredibly good use for chokecherries is wine; you will be quite pleased if you look into that aspect, as well.
Hope this helps -
Ron