Well, here it is. After a new, good, sharp end mill, lower depth of cut (to 0.020), RPMs to max (1775) a lot of WD-40 and about an hour and a half, here's what I ended up with:
I still need to mill down the top some to match the bottom (it turns out that my blank was 0.1 taller than I designed for), and then cut it in half (top to bottom through the middle - it's actually two identical parts).
Thanks for the help, Jim. You gave me a lot of practical advice on the settings and that made the difference. I'm trying to get a handle now understanding chip load and think I'm making progress. But what you said sure made a difference. Now I have parts I can use!