Very cool update, thanks for sharing. I haven't gone to that spot but passed by it a couple times. Glad you're getting some success!
Another place you might want to try is back down by Sylvan & Blackburn. If you park in the lot, then cross Blackburn north and walk a bit there's another spillway type pool just under the bridge. Might be worth a throw or two. The other spot is one another person here pointed out, that if you keep walking north on the sidewalk, eventually you'll come to a grassy area with some trees that opens to a pretty large pond like area. There's a couple houses across the way and a gazebo thing, so you'll know it when you see it. Could be pretty deep, might be a bit of work to throw through the trees though.
Keep at it!